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Snorkeling (British and Commonwealth English spelling: snorkelling) is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped breathing tube called a snorkel, and usually swimfins. In cooler waters, a wetsuit may also be worn. Use of this equipment allows the snorkeler to observe underwater attractions for extended periods with relatively little effort and to breathe while face-down at the surface.

Snorkeling is a popular recreational activity, particularly at tropicalresort locations. The primary appeal is the opportunity to observe underwater life in a natural setting without the complicated equipment and training required for scuba diving. It appeals to all ages because of how little effort there is, and without the exhaled bubbles of scuba-diving equipment. It is the basis of the two surface disciplines of the underwater sport of finswimming.^[1]

Snorkeling is also used by scuba divers when on the surface, in underwater sports such as underwater hockey and underwater rugby, and as part of water-based searches conducted by search and rescue teams.

• 1Snorkel
  • 1.3Separate snorkels
    • 1.3.1Typology
    • 1.3.2Construction
  • 1.4Integrated snorkels
    • 1.4.1Typology
    • 1.4.2Construction
• 2Diving mask
• 3Applications of snorkeling
• 4Practice of snorkeling
• 7References

Snorkel[edit]

A snorkel is a device used for breathing air from above the surface when the wearer's head is face downwards in the water with the mouth and the nose submerged. It may be either separate or integrated into a swimming or diving mask. The integrated version is only suitable for surface snorkeling, while the separate device may also be used for underwater activities such as spearfishing, freediving, finswimming, underwater hockey, underwater rugby and for surface breathing with scuba equipment. A swimmer's snorkel is a tube bent into a shape often resembling the letter 'L' or 'J', fitted with a mouthpiece at the lower end and constructed of light metal, rubber or plastic. The snorkel may come with a rubber loop or a plastic clip enabling the snorkel to be attached to the outside of the head strap of the diving mask. Although the snorkel may also be secured by tucking the tube between the mask-strap and the head, this alternative strategy can lead to physical discomfort, mask leakage or even snorkel loss.^[2]

To comply with the current European standardEN 1972 (2015), a snorkel for users with larger lung capacities should not exceed 38 centimeters in length and 230 cubic centimeters in internal volume, while the corresponding figures for users with smaller lung capacities are 35 cm and 150 cc respectively.^[3] Current World Underwater Federation (CMAS) Surface Finswimming Rules (2017) require snorkels used in official competitions to have a total length between 43 and 48 cm and to have an inner diameter between 1.5 and 2.3 cm.^[4] A longer tube would not allow breathing when snorkeling deeper, since it would place the lungs in deeper water where the surrounding water pressure is higher. The lungs would then be unable to inflate when the snorkeler inhales, because the muscles that expand the lungs are not strong enough to operate against the higher pressure.^[5] The pressure difference across the tissues in the lungs, between the blood capillaries and air spaces would increase the risk of pulmonary edema.

Snorkels constitute respiratory dead space. When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again, reducing the amount of fresh air in the inhaled volume, and increasing the risk of a buildup of carbon dioxide in the blood, which can result in hypercapnia. The greater the volume of the tube, and the smaller the tidal volume of breathing, the more this problem is exacerbated. A smaller diameter tube reduces the dead volume, but also increases resistance to airflow and so increases the work of breathing. Occasional exhalation through the nose while snorkeling will slightly reduce the buildup of carbon dioxide, and may help in keeping the mask clear of water. It may also increase fogging.

Operation[edit]

The simplest type of snorkel is a plain tube that is allowed to flood when underwater. The snorkeler expels water from the snorkel either with a sharp exhalation on return to the surface (blast clearing) or by tilting the head back shortly before reaching the surface and exhaling until reaching or breaking the surface (displacement method) and facing forward or down again before inhaling the next breath. The displacement method expels water by filling the snorkel with air; it is a technique that takes practice but clears the snorkel with less effort, but only works when surfacing. Clearing splash water while at the surface requires blast clearing.^[6]

Some snorkels have a sump at the lowest point to allow a small volume of water to remain in the snorkel without being inhaled when the snorkeler breathes. Some also have a non-return valve in the sump, to drain water in the tube when the diver exhales. The water is pushed out through the valve when the tube is blocked by water and the exhalation pressure exceeds the water pressure on the outside of the valve. This is almost exactly the mechanism of blast clearing which does not require the valve, but the pressure required is marginally less, and effective blast clearing requires a higher flow rate. The full face mask has a double airflow valve which allows breathing through the nose in addition to the mouth.^[7] A few models of snorkel have float-operated valves attached to the top end of the tube to keep water out when a wave passes, but these cause problems when diving as the snorkel must then be equalized during descent, using part of the diver's inhaled air supply. Some recent designs have a splash deflector on the top end that reduces entry of any water that splashes over the top end of the tube, thereby keeping it relatively free from water.^[8]

Finswimmers do not normally use snorkels with a sump valve, as they learn to blast clear the tube on most if not all exhalations, which keeps the water content in the tube to a minimum as the tube can be shaped for lower work of breathing, and elimination of water traps, allowing greater speed and lowering the stress of eventual swallowing of small quantities of water, which would impede their competition performance.^[9]

A common problem with all mechanical clearing mechanisms is their tendency to fail if infrequently used, or if stored for long periods, or through environmental fouling, or owing to lack of maintenance. Many also either slightly increase the flow resistance of the snorkel, or provide a small water trap, which retains a little water in the tube after clearing.^[10]

Modern designs use silicone rubber in the mouthpiece and one-way clearing and float valves due to its resistance to degradation and its long service life. Natural rubber was formerly used, but slowly oxidizes and breaks down due to ultraviolet light exposure from the sun. It eventually loses its flexibility, becomes brittle and cracks, which can cause clearing valves to stick in the open or closed position, and float valves to leak due to a failure of the valve seat to seal. In even older designs, some snorkels were made with small 'ping pong' balls in a cage mounted to the open end of the tube to prevent water ingress. These are no longer sold or recommended because they are unreliable and considered hazardous. Similarly, diving masks with a built-in snorkel are considered unsafe by scuba diving organizations such as PADI, BSAC because they can engender a false sense of security and can be difficult to clear if flooded.

Chronology and history[edit]

Snorkeling is mentioned by Aristotle in his Parts of Animals. He refers to divers using 'instruments for respiration' resembling the elephant's trunk.^[11] Some evidence suggests that snorkeling may have originated in Crete some 5,000 years ago as sea sponge farmers used hollowed out reeds to submerge and retrieve natural sponge for use in trade and commerce.^[12] In the fifteenth century, Leonardo da Vinci drew designs for an underwater breathing device consisting of cane tubes with a mask to cover the mouth at the demand end and a float to keep the tubes above water at the supply end.^[13][14] The following timeline traces the modern history of the swimmers' snorkel during the twentieth and twenty-first centuries.

1927: First use of swimmer's breathing tube and mask. According to Dr Gilbert Doukan's 1957 World Beneath the Waves^[15] and cited elsewhere,^[16] 'In 1927, and during each summer from 1927 to 1930, on the beach of La Croix-Valmer, Jacques O'Marchal could be seen using the first face mask and the first breathing tube. He exhibited them, in fact, in 1931, at the International Nautical Show. On his feet, moreover, he wore the first 'flippers' designed by Captain de Corlieu, the use of which was to become universal.'

1932: First submerged persons' breathing tube patent application filed. On 30 July 1932, Joseph L. Belcher files a patent application for 'breathing apparatus' delivering air to a submerged person by suction from the surface of the water through hoses connected to a float. His invention is granted US patent 1,901,219 on 14 March 1933.^[17]

1938: First swimmers’ mask with integrated breathing tubes. In 1938, French naval officer Yves Le Prieur introduces his 'Nautilus' full-face diving mask with hoses emerging from the sides and leading upwards to an air inlet device whose ball valve opens when it is above water and closes when it is submerged.^[18][19][20] In November 1940, American spearfisherman Charles H. Wilen files his 'swimmer’s mask' invention, which is granted US patent 2,317,237 of 20 April 1943.^[21] The device resembles a full-face diving mask incorporating two breathing tubes topped with valves projecting above the surface for inhalation and exhalation purposes. On 11 July 1944, he obtains US design patent 138,286 for a simpler version of this mask with a flutter valve at the bottom and a single breathing tube with a ball valve at the top.^[22] Throughout their heydey of the 1950s and early 1960s, masks with integrated tubes appear in the catalogues of American, Australian, British, French, German, Greek, Italian and Spanish swimming and diving equipment manufacturers. Meanwhile, in 1957, the US monthly product-testing magazine Consumer Reports concludes that 'snorkel-masks have some value for swimmers lying on the surface while watching the depths in water free of vegetation and other similar hazards, but they are not recommended for a dive 'into the blue'.^[23] According to an underwater swimming equipment review in the British national weekly newspaper The Sunday Times in December 1973, 'the mask with inbuilt snorkel is doubly dangerous (...) A ban on the manufacture and import of these masks is long overdue in Britain'.^[24] In a decree of 2 August 1989,^[25] the French government suspends the manufacture, importation and marketing of ball-valve snorkel-masks. By the noughties, just two swim masks with attached breathing tubes remain in production worldwide: the Majorca sub 107S single-snorkel model^[26] and the Balco 558 twin-snorkel full-face model,^[27] both manufactured in Greece. In May 2014, the French Decathlon company files its new-generation full-face snorkel-mask design, which is granted US design patent 775,722^[28] on 3 January 2017, entering production as the 'Easybreath' mask (see Figure 3) designated for surface snorkeling only.

1938: First front-mounted swimmer's breathing tube patent filed. In December 1938, French spearfisherman Maxime Forjot and his business partner Albert Méjean file a patent application in France for a breathing tube worn on the front of the head over a single-lens diving mask enclosing the eyes and the nose and it is granted French patent 847848 on 10 July 1939.^{[29][30][31][32]} In July 1939, Popular Science magazine publishes an article containing illustrations of a spearfisherman using a curved length of hosepipe as a front-mounted breathing tube and wearing a set of swimming goggles over his eyes and a pair of swimming fins on his feet.^[33] In the first French monograph on spearfishing La Chasse aux Poissons (1940), medical researcher and amateur spearfisherman Dr Raymond Pulvénis illustrates his 'Tuba', a breathing tube he designed to be worn on the front of the head over a single-lens diving mask enclosing the eyes and the nose. Francophone swimmers and divers have called their breathing tube 'un tuba' ever since. In 1943, Raymond Pulvénis and his brother Roger obtain a Spanish patent for their improved breathing tube mouthpiece design.^[34] In 1956, the UK diving equipment manufacturer E. T. Skinner (Typhoon) markets a 'frontal' breathing tube with a bracket attachable to the screw at the top of an oval diving mask.^[35] Although it falls out of favour with underwater swimmers eventually, the front-mounted snorkel becomes the breathing tube of choice in competitive swimming and finswimming (see Figure 4) because it contributes to the swimmer's hydrodynamic profile.

1939: First side-mounted swimmers’ breathing tube patent filed. In December 1939, expatriate Russian spearfisherman Alexandre Kramarenko files a patent in France for a breathing tube worn at the side of the head with a ball valve at the top to exclude water and a flutter valve at the bottom. Kramarenko and his business partner Charles H. Wilen refile the invention in March 1940 in the USA, where their 'underwater apparatus for swimmers' is granted US patent 2,317,236 on 20 April 1943;^[36] after entering production in France, the device is called 'Le Respirator'.^[37] The co-founder of ScubaproDick Bonin is credited with the introduction of the flexible-hose snorkel in the mid-1950s and the exhaust valve to ease snorkel clearing in 1980.^[38] In 1964, US Divers markets an L-shaped snorkel designed to outperform J-shaped models by increasing breathing ease, cutting water drag and eliminating the 'water trap'.^[39] In the late 1960s, Dacor launched a 'wraparound big-barrel' contoured snorkel, which closely follows the outline of the wearer's head and comes with a wider bore to improve airflow.^[40] The findings of the 1977 report 'Allergic reactions to mask skirts, regulator mouthpieces and snorkel mouthpieces'^[41] encourage diving equipment manufacturers to fit snorkels with hypoallergenic gum rubber and medical-grade silicone mouthpieces (see Figure 5). In the world of underwater swimming and diving, the side-mounted snorkel has long become the norm, although new-generation full-face swim masks with integrated snorkels are beginning to grow in popularity for use in floating and swimming on the surface.

1950: First use of 'snorkel' to denote a breathing device for swimmers. In November 1950, the Honolulu Sporting Goods Co. introduces a 'swim-pipe' resembling Kramarenko and Wilen’s side-mounted ball- and flutter-valve breathing tube design, urging children and adults to 'try the human version of the submarine snorkel and be like a fish'.^[42] Every advertisement in the first issue of Skin Diver magazine in December 1951^[43] uses the alternative spelling 'snorkles' to denote swimmers’ breathing tubes. In 1955, Albert VanderKogel classes stand-alone breathing tubes and swim masks with integrated breathing tubes as 'pipe snorkels' and 'mask snorkels' respectively.^[44] In 1957, the British Sub-Aqua Club journal features a lively debate about the standardisation of diving terms in general and the replacement of the existing British term 'breathing tube' with the American term 'snorkel' in particular.^[45] The following year sees the première of the 1958 British thriller film The Snorkel, whose title references a diving mask topped with two built-in breathing tubes. To date, every national and international standard on snorkels uses the term 'snorkel' exclusively.

1969: First national standard on snorkels. In December 1969, the British Standards Institution publishes British standardBS 4532 entitled 'Specification for snorkels and face masks'^[46] and prepared by a committee on which the British Rubber Manufacturers' Association, the British Sub-Aqua Club, the Department for Education and Science, the Federation of British Manufacturers of Sports and Games, the Ministry of Defence Navy Department and the Royal Society for the Prevention of Accidents are represented. This British standard sets different maximum and minimum snorkel dimensions for adult and child users, specifies materials and design features for tubes and mouthpieces and requires a warning label and a set of instructions to be enclosed with each snorkel. In February 1980 and June 1991, the Deutsches Institut für Normung publishes the first and second editions of German standardDIN 7878 on snorkel safety and testing.^[47] This German standard sets safety and testing criteria comparable to British standard BS 4532 with an additional requirement that every snorkel must be topped with a fluorescent red or orange band to alert other water users of the snorkeller's presence. In November 1988, the Austrian Standards Institute publishes Austrian standard ÖNORM S 4223^[48] entitled 'Tauch-Zubehör; Schnorchel; Abmessungen, sicherheitstechnische Anforderungen, Prüfung, Normkennzeichnung' in German, subtitled 'Diving accessories; snorkel; dimensions, safety requirements, testing, marking of conformity' in English and closely resembling German Standard DIN 7878 of February 1980 in specifications. The first and second editions of European standardEN 1972 on snorkel requirements and test methods^[49] appear in July 1997 and December 2015. This European standard refines snorkel dimension, airflow and joint-strength testing and matches snorkel measurements to the user's height and lung capacity. The snorkels regulated by these British, German and European standards exclude combined masks and snorkels in which the snorkel tubes open into the mask.

Separate snorkels[edit]

A snorkel may be either separate or integrated into a swim or dive mask. Usage of the term 'snorkel' in this section excludes devices integrated with, and opening into, swimmers' or divers' masks.

A separate snorkel typically comprises a tube for breathing and a means of attaching the tube to the head of the wearer. The tube has an opening at the top and a mouthpiece at the bottom. Some tubes are topped with a valve to prevent water from entering the tube when it is submerged.

Typology[edit]

Although snorkels come in many forms, they are primarily classified by their dimensions and secondarily by their orientation and shape. The length and the inner diameter (or inner volume) of the tube are paramount health and safety considerations when matching a snorkel to the morphology of its end-user. The orientation and shape of the tube must also be taken into account when matching a snorkel to its end use while seeking to optimise ergonomic factors such as streamlining, airflow and water retention.

Dimensions[edit]

The total length, inner diameter and/or inner volume of a snorkel tube are matters of utmost importance because they affect the user's ability to breathe normally while swimming or floating head downwards on the surface of the water. These dimensions also have implications for the user's ability to blow residual water out of the tube when surfacing. An overlong snorkel tube may cause breathing resistance, while an overwide tube may prove hard to clear of water. A high-volume tube is liable to encourage a build-up of stale air, including exhaled carbon dioxide, because it constitutes respiratory dead space.

To date, all national and international standards on snorkels specify two ranges of tube dimensions to meet the health and safety needs of their end-users, whether young or old, short or tall, with low or high lung capacity (See Figure 1 and Figure 2). The snorkel dimensions at issue are the total length, the inner diameter and/or the inner volume of the tube. The specifications of the standardisation bodies are tabulated below.

The table above shows how snorkel dimensions have changed over time in response to progress in swimming and diving science and technology:

• Maximum tube length has almost halved (from 600 to 380 mm).
• Maximum bore (inner diameter) has increased (from 18 to 25 mm).
• Capacity (or inner volume) has partly replaced inner diameter when dimensioning snorkels.
• Different snorkel dimensions have evolved for different users (first adults/children; then taller/shorter heights; then larger/smaller lung capacities).

Orientation and shape[edit]

Snorkels come in two orientations: Front-mounted (see Figure 4) and side-mounted (see Figure 5). The first snorkel to be patented in 1938 was front-mounted, worn with the tube over the front of the face and secured with a bracket to the diving mask. Front-mounted snorkels proved popular in European snorkeling until the late 1950s, when side-mounted snorkels came into the ascendancy. Front-mounted snorkels experienced a comeback a decade later as a piece of competitive swimming equipment to be used in pool workouts and in finswimming races, where they outperform side-mounted snorkels in streamlining. Front-mounted snorkels are attached to the head with a special head bracket fitted with straps to be adjusted and buckled around the temples (see Figure 4).

Side-mounted snorkels are generally worn by scuba divers on the left-hand side of the head because the scuba regulator is placed over the right shoulder. They come in at least four basic shapes (see Figure 6): J-shaped; L-shaped; Flexible-hose; Contour.^[50]

• A. J-shaped snorkels represent the original side-mounted snorkel design, cherished by some for their simplicity but eschewed by others because water accumulates in the U-bend at the bottom.
• B. L-shaped snorkels represent an improvement on the J-shaped style. They claim to reduce breathing resistance, to cut water drag and to remove the 'water trap'.
• C. Flexible-hose snorkels curry favour with some scuba divers because the flexible hose between the tube and the mouthpiece causes the lower part of the snorkel to drop out of the way when it is no longer in use. However, a spearfisher equipped with this snorkel must have a hand spare to replace the mouthpiece when it falls out of the mouth.
• D. Contour snorkels represent the most recent design. They have a 'wraparound' shape with smooth curves closely following the outline of the wearer's head, which improves wearing comfort.

Construction[edit]

A snorkel consists essentially of a tube with a mouthpiece to be inserted between the lips. See Figure 7 for snorkel parts location and nomenclature.

Barrel[edit]

The barrel is the hollow tube leading from the supply end at the top of the snorkel to the demand end at the bottom where the mouthpiece is attached. The barrel is made of a relatively rigid material such as plastic, light metal or hard rubber. The bore is the interior chamber of the barrel; bore length, diameter and bends all affect breathing resistance.

The top of the barrel may be open to the elements or fitted with a valve designed to shut off the air supply from the atmosphere when the top is submerged (see Figure 5 and Figure 7). There may be a fluorescent red or orange band around the top to alert other water users of the snorkeller's presence. The simplest way of attaching the snorkel to the head is to slip the top of the barrel between the mask strap and the head. This may cause the mask to leak, however, and alternative means of attachment of the barrel to the head can be seen in Figure 8.

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• A. The mask strap is threaded through the permanent plastic loop moulded on to the centre of the barrel.
• B. The mask strap is threaded through the separable rubber loop pulled down to the centre of the barrel.
• C. The rubber band knotted to the centre of the barrel is stretched over the temple. This method was last used in the USA during the 1950s.
• D. The mask strap is threaded through the rotatable plastic snorkel keeper positioned at the centre of the barrel.

Mouthpiece[edit]

Attached to the demand end of the snorkel at the bottom of the barrel, the mouthpiece serves to keep the snorkel in the mouth. It is made of soft and flexible material, typically natural rubber and latterly silicone or PVC. The commonest of the multiple designs available^[51] features a slightly concave flange with two lugs to be gripped between the teeth (see Figure 9):

• A. Flanged mouthpiece with twin lugs at end of length of flexible corrugated hose designed for flexible-hose snorkel.
• B. Flanged mouthpiece with twin lugs at the end of short neck designed for J-shaped snorkel.
• C. Flanged mouthpiece with twin lugs positioned at a right angle and designed for an L-shaped snorkel.
• D. Flanged mouthpiece with twin lugs at the end of a flexible U-shaped elbow designed to be combined with a straight barrel to create a J-shaped snorkel.
• E. Flanged mouthpiece with twin bite plates offset at an angle from a contoured snorkel.

A disadvantage of mouthpieces with lugs is the presence of the teeth when breathing. The tighter the teeth grip the mouthpiece lugs, the smaller the air gap between the teeth and the harder it will be to breathe.

Additional features[edit]

Snorkel design is only limited by the imagination. Among recent innovations is the 'collapsible snorkel', which can be folded up in a pocket for emergencies.^[52] One for competitive swimmers is a lightweight lap snorkel; with twin tubes^[53] another is a 'restrictor cap' placed inside a snorkel barrel 'restricting breathing by 40% to increase cardiovascular strength and build lung capacity'.^[54] Some additional snorkel features such as shut-off and drain valves fell out of favour decades ago, only to return in the contemporary era as more reliable devices for incorporation into 'dry' and 'semi-dry' snorkels; see Figure 5 featuring a modern snorkel topped with a splash guard.^[55]

Integrated snorkels[edit]

In this section, usage of the term 'snorkel' denotes single or multiple tubular devices integrated with, and opening into, a swim or dive mask, while the term 'snorkel-mask' is used to designate a swim or dive mask with single or multiple built-in snorkels. Such snorkels from the past typically comprised a tube for breathing and a means of connecting the tube to the space inside the snorkel-mask. The tube had an aperture with a shut-off valve at the top and opened at the bottom into the mask, which might cover the mouth as well as the nose and eyes. Although such snorkels tended to be permanent fixtures on historical snorkel-masks, a minority could be detached from their sockets and replaced with plugs enabling certain snorkel-masks to be used without their snorkels (see Figure 10).

The 1950s were the heyday of older-generation snorkel-masks, first for the pioneers of underwater hunting and then for the general public who swam in their wake. One even-minded authority of the time declared that 'the advantage of this kind of mask is mainly from the comfort point of view. It fits snugly to one's face, there is no mouthpiece to bite on, and one can breathe through either nose or mouth'.^[56] Another concluded with absolute conviction that 'built-in snorkel masks are the best' and 'a must for those who have sinus trouble.'^[57] Yet others, including a co-founder of the British Sub-Aqua Club, deemed masks with integrated snorkels to be complicated and unreliable: 'Many have the breathing tube built in as an integral part of the mask. I have never seen the advantage of this, and this is the opinion shared by most experienced underwater swimmers I know'.^[58] Six decades on, a new generation of snorkel-masks has come to the marketplace (see Figure 3).

Typology[edit]

Like separate snorkels, integrated snorkels come in a variety of forms. The assortment of older-generation masks with integrated snorkels in Figure 10 highlights certain similarities and differences:

• A. A model enclosing the eyes and the nose only. A permanent single snorkel emerges from the top of the mask and terminates above with a shut-off ball valve.
• B. A model with a chinpiece to enclose the eyes, the nose and the mouth. Permanent twin snorkels emerge from either side of the mask and terminate above with shut-off 'gamma' valves.
• C. A model enclosing the eyes and the nose only. Removable twin snorkels emerge from either side of the mask and terminate above with shut-off ball valves. Supplied with plugs for use without snorkels, as illustrated.

Integrated snorkels are tentatively classified here by their tube configuration and by the face coverage of the masks to which they are attached.

Tube configuration[edit]

As a rule, early manufacturers and retailers classed integrated snorkel masks by the number of breathing tubes projecting from their tops and sides. Their terse product descriptions often read: 'single snorkel mask', 'twin snorkel mask', 'double snorkel mask' or 'dual snorkel mask'.^[59]

Face coverage[edit]

All existing new-generation snorkel-masks (see Figure 3) are full-face masks covering the eyes, the nose and the mouth. They enable surface snorkellers to breathe nasally or orally and may be a workaround in the case of surface snorkellers who gag in response to the presence of standard snorkel mouthpieces in their mouths. Some old-generation snorkel-masks (See Figure 11) are full-face masks covering the eyes, nose and mouth, while others exclude the mouth, covering the eyes and the nose only. The 1950s US Divers 'Marino' hybrid comprised a single snorkel mask with eye and nose coverage and a separate snorkel for the mouth.^[60]

Construction[edit]

An integrated snorkel consists essentially of a tube topped with a shut-off valve and opening at the bottom into the interior of a diving mask.

Tube[edit]

Tubes are made of strong but lightweight materials such as plastic. At the supply end, they are fitted with valves made of plastic, rubber or latterly silicone. Three typical shut-off valves are illustrated in Figure 11.

• A. Ball valve using a ping-pong ball in a cage to prevent water ingress when submerged. This device may be the most common and familiar valve used atop old-generation snorkels, whether separate or integrated.
• B. Hinged 'gamma' valve to prevent water ingress when submerged. This device was invented in 1954 by Luigi Ferraro, fitted as standard on every Cressi-sub mask with integrated breathing tubes and granted US patent 2,815,751 on 10 December 1957.^[61]
• C. Sliding float valve to prevent water ingress when submerged. This device was used on Britmarine brand snorkels manufactured by the Haffenden company in Sandwich, Kent during the 1960s.

Integrated snorkels must be fitted with valves to shut off the snorkel's air inlet when submerged. Water will otherwise pour into the opening at the top and flood the interior of the mask. Snorkels are attached to sockets on the top or the sides of the mask.

Mask[edit]

The skirt of the diving mask attached to the snorkel is made of rubber, or latterly silicone. Older-generation snorkel masks come with a single oval, round or triangular lens retained by a metal clamp in a groove within the body of the mask. An adjustable head strap or harness ensures a snug fit on the wearer's face. The body of a mask with full-face coverage is fitted with a chinpiece to enable a complete leaktight enclosure of the mouth.

Additional features[edit]

Older proprietary designs came with special facilities. One design separated the eyes and the nose into separate mask compartments to reduce fogging. Another enabled the user to remove integrated snorkels and insert plugs instead, thus converting the snorkel-mask into an ordinary diving mask. New-generation snorkel-masks enclose the nose and the mouth within an inner mask at the demand end directly connected to the single snorkel with its valve at the supply end.

Diving mask[edit]

Snorkelers normally wear the same kind of mask as those worn by scuba divers. By creating an airspace, the mask enables the snorkeler to see clearly underwater. All scuba diving masks consist of the lenses also known as a faceplate, a soft rubber skirt, which encloses the nose and seals against the face, and a head strap to hold it in place. There are different styles and shapes. These range from oval shaped models to lower internal volume masks and may be made from different materials; common choices are silicone and rubber. A snorkeler who remains at the surface can use swimmer's goggles which do not enclose the nose.

Full-face snorkel mask[edit]

Full face snorkel masks use an integral snorkel with separate channels for intake and exhaled gases theoretically ensuring the user is always breathing untainted fresh air whatever the respiratory effort. The main difficulty or danger is that it must fit the whole face perfectly and since no two faces are the same shape, it should be used with great care and in safe water. In the event of accidental flooding, the whole mask must be removed to continue breathing. Unless the snorkeler is able to equalize without pinching their nose it can only be used on the surface, or a couple of feet below since the design makes it impossible to pinch the nose in order to equalise pressure at greater depth. Trained scuba divers are likely to avoid such devices^{[citation needed][clarification needed]} however snorkel masks are a boon for those with medical conditions that preclude taking part in SCUBA diving.^{[citation needed][clarification needed]}

As a result of a short period with an unusually high number of snorkeling deaths in Hawaii^[62] there is some suspicion that the design of the masks can result in buildup of excess CO². It is far from certain that the masks are at fault, but the state of Hawaii has begun to track the equipment being used in cases of snorkeling fatalities. Besides the possibility that the masks, or at least some brands of the mask, are a cause other theories include the possibility that the masks make snorkeling accessible to people who have difficulty with traditional snorkeling equipment. That ease of access may result in more snorkelers who lack experience or have underlying medical conditions, possibly exacerbating problems that are unrelated to the type of equipment being used.^[63]

Applications of snorkeling[edit]

Snorkeling is an activity in its own right, as well as an adjunct to other activities, such as breath-hold diving, spearfishing and scuba diving,^[64] and several competitive underwater sports, such as underwater hockey and finswimming.

In all cases, the use of a snorkel facilitates breathing while swimming at the surface and observing what is going on under the water.

Scuba diving[edit]

A snorkel can be useful when scuba diving as it is a safe way of swimming face down at the surface for extended periods to conserve the bottled air supply, or in an emergency situation when there is a problem with either air supply or regulator.^[64] Many dives do not require the use of a snorkel at all, and some scuba divers do not consider a snorkel a necessary or even useful piece of equipment, but the usefulness of a snorkel depends on the dive plan and the dive site. If there is no requirement to swim face down and see what is happening underwater, then a snorkel is not useful. If it is necessary to swim over heavy seaweed which can entangle the pillar valve and regulator if the diver swims face upward to get to and from the dive site, then a snorkel is useful to save breathing gas.

Practice of snorkeling[edit]

Being non-competitive, snorkeling is considered more a leisure activity than a sport.^[65] Snorkeling requires no special training, only the very basic swimming abilities and being able to breathe through the snorkel.^[66] Some organizations^{[by whom?]} recommend that for snorkeling safety one should not snorkel alone,^[67] but rather with a 'buddy', a guide or a tour group.^{[citation needed]}

Some commercial snorkeling organizations require snorkelers at their venue to wear an inflatable vest, similar to a personal flotation device. They are usually bright yellow or orange and have a device that allows users to inflate or deflate the device to adjust their buoyancy. However, these devices hinder and prevent a snorkeler from free diving to any depth. Especially in cooler water, a wetsuit of appropriate thickness and coverage may be worn; wetsuits do provide some buoyancy without as much resistance to submersion. In the tropics, snorkelers (especially those with pale skin) often wear a rashguard or a shirt and/or board shorts in order to help protect the skin of the back and upper legs against sunburn.^{[citation needed]}

Experienced snorkelers may progress to amateur free-diving, which should be preceded by at least some training from a dive instructor or experienced free-diver.^{[citation needed]}

Safety precautions[edit]

The greatest danger to snorkelers are inshore and leisure craft such as jet skis, speed boats and the like. A snorkeler is often submerged in the water with only the tube visible above the surface. Since these craft can ply the same areas snorkelers visit, the chance for accidental collisions exists. Sailboats and sailboards are a particular hazard as their quiet propulsion systems may not alert the snorkeler of their presence. A snorkeler may surface underneath a vessel and/or be struck by it. Few locations demarcate small craft areas from snorkeling areas, unlike that done for regular beach-bathers, with areas marked by buoys. Snorkelers may therefore choose to wear bright or highly reflective colors/outfits and/or to employ dive flags to enable easy spotting by boaters and others.^{[citation needed]}

Snorkelers' backs, ankles, and rear of their thighs can be exposed to the sun for extended periods, and can burn badly (even if slightly submerged), without being noticed in time. The wearing appropriate covering such as a 'rash guard' with SPF (in warmer waters), a T-shirt, a wetsuit, and especially 'waterproof' sunblock will mitigate this risk.^{[citation needed]}

Dehydration is another concern. Hydrating well before entering the water is highly recommended, especially if one intends to snorkel for several hours. Proper hydration also prevents cramps. Snorkelers who hyperventilate to extend sub-surface time can experience hypocapnia if they hyperventilate prior to submerging. This can in turn lead to 'shallow water blackout'. Snorkeling with a buddy and remaining aware of the buddy's condition at all times can help avoid these difficulties.^{[citation needed]}

When snorkeling on or near coral reefs, care must be exercised to avoid contact with the delicate (and sometimes sharp or stinging) coral, and its poisonous inhabitants, usually by wearing protective gloves and being careful of one's environment. Coral scrapes and cuts often require specialized first aid treatment and potentially, emergency medical treatment to avoid infection. Booties and surf shoes are especially useful as they allow trekking over reefs exposed by low tide, to access drop-offs or deeper waters of the outer reef - this is, however, ecologically irresponsible.^{[citation needed]}

Contact with coral should always be avoided, because even boulder corals are fragile.

Another safety concern is interaction and contact with the marine life during encounters. While seals and sea turtles can seem harmless and docile, they can become alarmed if approached or feel threatened. Some creatures, like moray eels, can hide in coral crevices and holes and will bite fingers when there is too much prodding going on. For these reasons, snorkeling websites often recommend an 'observe but don't touch' etiquette when snorkeling.^[68]

Snorkeling locations[edit]

Snorkeling is possible in almost any body of water, but snorkelers are most likely to be found in locations where there are minimal waves, warm water, and something particularly interesting to see near the surface.^{[citation needed]}

Generally shallow reefs ranging from sea level to 1 to 4 meters (3 to 13 ft) are favored by snorkelers. Deeper reefs can also be explored, but repeated breath-holding to dive to those depths limits the number of practitioners, and raises the bar on the required fitness and skill level. Risk increases with increased depth and duration of the breath-hold excursions from the surface.^{[citation needed]}

Variants and related activities[edit]

• Bog snorkeling: An individual sport, popular in the United Kingdom and Australia.
• Finswimming: An individual sport, the most popular competitive sport of CMAS, the only of this federation present in World Games. Finswimmers use a slightly different snorkel, suited for hydrodynamics and speed.
• Free-diving: Any form of diving without breathing apparatus, but often referring to competitive apnea as a sport.
• Scuba diving: A form of untethered diving using a self-contained portable breathing apparatus, frequently as a pastime.
• Spearfishing: Fishing with a spear often with snorkeling equipment, either for competitive sport or to obtain food.
• Underwater hockey: A competitive team-sport played in swimming pools using snorkeling equipment, sticks and a puck.
• Underwater rugby: A competitive team-sport played in deeper swimming pools using snorkeling equipment, baskets and a ball.

Scientific opportunities[edit]

Underwater photography has become more and more popular since the early 2000s, resulting on millions of pictures posted every year on various websites and social media. This mass of documentation is endowed with an enormous scientific potential, as millions of tourists possess a much superior coverage power than professional scientists, who can not allow themselves to spend so much time in the field. As a consequence, several participative sciences programs have been developed, supported by geo-localization and identification web sites, along with protocols for auto-organization and self-teaching aimed at biodiversity-interested snorkelers, in order for them to turn their observations into sound scientific data, available for research. This kind of approach has been successfully used in Réunion island, allowing for tens of new records and even new species.^[69]

See also[edit]

References[edit]

1. ^FINSWIMMING - CMAS RULES VERSION 2012/03 In force as from January 1st 2013 (BoD179 - 22/11/2012). Rome: Confédération Mondiale des Activités Subaquatiques. 2012. pp. 3–4.
2. ^Steve Blount and Herb Taylor, The Joy of Snorkeling, New York, NY: Pisces Book Company, 1984, p. 21.
3. ^British Standards Institution: BS EN 1972: Diving equipment - Snorkels - Requirements and test methods, London: British Standards Institution, 2015.
4. ^CMAS Finswimming Rules Version 2017/01, p. 6. Retrieved on 19 February 2019 at http://www.cmas.org/finswimming/documents-of-the-finswimming-commission.
5. ^R. Stigler, 'Die Taucherei' in Fortschritte der naturwissenschaftlichen Forschung, IX. Band, Berlin/Wien, 1913.
6. ^Underwater World, Unit 3- Diving Skills. Retrieved on 28 February 2019 at https://www.diveunderwaterworld.com/s/Chapter-3-Diving-Skills.pdf.
7. ^Snorkel Ken, 'Full Face Snorkel Mask Reviews | Tribord EasyBreathe Alternatives and Best Prices'. Retrieved on 3 March 2019 at https://snorkelstore.net/full-face-snorkel-mask-review-lower-price-lower-quality/.
8. ^US patent 5,404,872, Splash-guard for snorkel tubes, April 11, 1995. Retrieved on 1 March 2019 at https://patentimages.storage.googleapis.com/01/fe/9a/6038e50865f3f1/US5404872.pdf.
9. ^Finswimming snorkels. Retrieved on 1 March 2019 at https://monofin.co.uk/blog-snorkels.html
10. ^Snorkel Care. Retrieved on 1 March 2019 at https://www.scubadoctor.com.au/care-snorkel.htm.
11. ^Ogle, W. 'Aristotle on the parts of animals, tr. with notes by W. Ogle'. Internet Archive. Retrieved 20 May 2013. Just then as divers are sometimes provided with instruments for respiration, through which they can draw air from above the water, and thus may remain for a long time under the sea, so also have elephants been furnished by nature with their lengthened nostril; and, whenever they have to traverse the water, they lift this up above the surface and breathe through it.
12. ^'Mediterranean commercial sponges: over 5000 years of natural history and cultural heritage'(PDF). Retrieved 2015-08-25.
13. ^British Library: Online gallery. Leonardo da Vinci. Diving Apparatus, http://www.bl.uk/onlinegallery/features/leonardo/diving.html. Retrieved on 13 February 2019.
14. ^Buceo Ibérico: El traje de buceo de Leonardo da Vinci, http://www.buceoiberico.com/mundo-submarino/el-traje-de-buceo-de-leonardo-da-vinci/. Retrieved on 13 February 2019.
15. ^Gilbert Doukan: World Beneath the Waves, New York, NY: John De Graff, Inc, 1957, p. 23. Full-text document retrieved on 20 February 2019 at https://archive.org/stream/worldbeneaththew009216mbp/worldbeneaththew009216mbp_djvu.txt.
16. ^See, for example, Faustolo Rambelli: 'Sulle maschere da sub, e qualche autorespiratore, ante II G. M.', HDS Notizie No. 28 November 2003, p. 19. Retrieved on 20 February 2019 at https://www.hdsitalia.org/sites/www.hdsitalia.org/files/documenti/HDSN28.pdf.
17. ^US Patent 1,901,219, Breathing apparatus, https://patentimages.storage.googleapis.com/4c/e6/a1/929022724fa381/US1901219.pdf. Retrieved on 27 February 2019.
18. ^Alain Perrier: 250 Réponses aux questions du plongeur curieux, Editions de Gerfaut, 2008, p. 70.
19. ^Un masque français révolutionnaire. Retrieved on 18 February 2019 at https://le-scaphandrier.blog4ever.com/un-masque-francais-revolutionnaire.
20. ^Le Scaphandre, découverte d'un nouveau monde. Retrieved on 19 February 2019 at http://cmaexpositions.canalblog.com/archives/2017/10/02/35731257.html.
21. ^US Patent 2,317,237: Swimmer's mask, https://patentimages.storage.googleapis.com/ac/ac/62/5802eccace1c6f/US2317237.pdf. Retrieved on 13 February 2019.
22. ^US Design Patent 138,286, Swimmer's mask, https://patentimages.storage.googleapis.com/3c/a0/78/52b889e518fbd1/USD138286.pdf. Retrieved on 13 February 2019.
23. ^'Underwater swimming equipment', Consumer Reports, Vol. 22 No. 7 (July 1957), pp. 324-330.
24. ^Adam Hopkins: 'Into the undersea world', The Sunday Times, 20 December 1973, p. 45.
25. ^Arrêté du 2 août 1989 portant suspension de la fabrication, de l’importation, de la mise sur le marché et ordonnant le retrait des masques de plongée comportant un tube incorporé muni d’une balle de ping-pong, https://www.legifrance.gouv.fr/jo_pdf.do?id=JORFTEXT000000300898. Retrieved on 13 February 2019.
26. ^https://web.archive.org/web/20140822173444/http://www.majorcasub.gr/. Retrieved on 19 February 2019.
27. ^https://www.fishingmegashop.com/balco-mask-558.html. Retrieved on 19 February 2019.
28. ^US Design Patent 775,722, Mask with snorkel, https://patentimages.storage.googleapis.com/c7/05/bd/f253e240db3b0a/USD775722.pdf. Retrieved on 13 February 2019.
29. ^French patent 847848, Masque pour l'exploration sous-marine avec visibilité normale et toutes autres applications Brevet d'invention, Ministère du Commerce et de l'Industrie, France.
30. ^Pierre de Latil (1949) 'Masques et respirateurs sous-marins', Le Chasseur Français N°630, August 1949, p. 621. Retrieved on 13 February 2019 at http://perso.numericable.fr/cf40/articles/4849/4849621A.htm
31. ^http://forum.historische-tauchergesellschaft.de/viewtopic.php?p=2767&sid=b53d333e6aa2f375ba19a0f8c7dad01c. Retrieved on 13 February 2019.
32. ^Divernet: The ripping-off of Maxime's mask. Retrieved on 13 February 2019 at http://archive.divernet.com/general-diving/p302270-the-ripping-off-of-maximes-mask.html
33. ^http://blog.modernmechanix.com/human-submarine-shoots-fish-with-arrows/. Retrieved on 13 February 2019.
34. ^https://patentados.com/19430301/131/. Retrieved on 13 February 2019.
35. ^'Combined mask-tube', Neptune, Vol. 1 No. 3 (January 1956), p. 23.
36. ^ US Patent 2,317,236, Breathing apparatus for swimmers, https://patentimages.storage.googleapis.com/63/40/8a/e556c7ec105900/US2317236.pdf. Retrieved on 13 February 2019.
37. ^Robert Devaux: Initiation à la chasse sous-marine, Cannes: Imprimerie Robaudy, 1947, p. 64.
38. ^Bret Gilliam: Dick Bonin, founder of Scubapro. Retrieved on 17 February 2019 at https://www.tdisdi.com/diving-pioneers-and-innovators/dick-bonin/.
39. ^US Divers 1964 catalogue. Retrieved on 17 February 2019 from Gear info: Manuals and Catalogs at http://www.vintagedoublehose.com/forum/.
40. ^Dacor diving equipment guide 1968. Retrieved on 17 February 2019 at http://www.cg-45.com/downloads/download.php?file=Catalogs/DACOR/Dacor%201968.pdf.
41. ^John E. Alexander: 'Allergic reactions to mask skirts, regulator mouthpieces and snorkel mouthpieces', Journal of the South Pacific Underwater Medicine Society Vol. 7 No. 2 (1977), pp. 44-45. Retrieved on 16 February 2019 at http://archive.rubicon-foundation.org/xmlui/bitstream/handle/123456789/6144/SPUMS_V7N2_10.pdf.
42. ^Honolulu Star-Bulletin (Honolulu, Hawaii), Friday, November 10, 1950, p. 21.
43. ^http://www.divinghistory.org/wp-content/uploads/2015/08/skin-diver-first-issue-1951.pdf. Retrieved on 13 February 2019.
44. ^Albert VanderKogel with Rex Lardner: Underwater sport, New York: Henry Holt and Company, 1955, pp. 22-26.
45. ^Alan Broadhurst: 'Let's get it right', Triton Vol. 2 No. 3 (May-June 1957), pp. 20-21. G. F. Brookes: 'Watch your language', Triton Vol. 2 No. 4 (July-August 1957), p. 12.
46. ^British Standards Institution: BS 4532: Specification for snorkels and face masks. London: British Standards Institution, 1969. Amendment Slip No. 1 to BS 4532:1969 Snorkels and face masks, 30 December 1977.
47. ^Deutsches Institut für Normung: DIN 7878: Tauch-Zubehör: Schnorchel. Maße. Anforderungen. Prüfung (Diving accessories for skin divers; snorkel; technical requirements of safety, testing), Berlin/Cologne: Beuth Verlag, 1980. Deutsches Institut für Normung: DIN 7878: Tauch-Zubehör: Schnorchel. Sicherheitstechnische Anforderungen und Prüfung (Diving accessories for skin divers; snorkel; safety requirements and testing), Berlin/Cologne: Beuth Verlag, 1991.
48. ^Austrian Standards Institute: ÖNORM S 4223: Tauch-Zubehör; Schnorchel; Abmessungen, sicherheitstechnische Anforderungen, Prüfung, Normkennzeichnung. Diving accessories; snorkel; dimensions, safety requirements, testing, marking of conformity, Vienna: Austrian Standards Institute, 1988.
49. ^British Standards Institution: BS EN 1972: Diving accessories - Snorkels - Safety requirements and test methods, London: British Standards Institution, 1997. British Standards Institution: BS EN 1972: Diving equipment - Snorkels - Requirements and test methods, London: British Standards Institution, 2015.
50. ^PADI Diver Manual. Santa Ana, CA: PADI, 1983, p. 17.
51. ^P. P. Serebrenitsky: Техника подводного спорта, Lenizdat, 1969, p. 92. Full text retrieved on 22 February, 2019 at http://ilovediving.ru/articles/maski-polumaski-ochki-dykhatelnye-trubki-lasty.
52. ^https://www.scuba-diving-smiles.com/folding-snorkel.html. Retrieved on 22 February 2019.
53. ^https://www.swimoutlet.com/p/ameo-powerbreather-lap-snorkel-8148117. Retrieved on 22 February 2019.
54. ^http://www.michaelphelps.com/us/equipment/equipment-focus-restrictor-cap. Retrieved on 22 February 2019.
55. ^US patent 5,404,872, Splash-guard for snorkel tubes, April 11, 1995. Retrieved on 1 March 2019 at https://patentimages.storage.googleapis.com/01/fe/9a/6038e50865f3f1/US5404872.pdf.
56. ^Simon Codrington: Guide to underwater hunting, London: Adlard Coles, 1954, pp. 17-18.
57. ^Cornel Lumière: Beneath the seven seas, London: Hutchinson, 1956, pp. 18-20, 30.
58. ^Peter Small: Your guide to underwater adventure, London: Lutterworth Press, 1957, p. 5.
59. ^Early Mfg. & Retailers - Florida Frogman No.19. Retrieved on 26 February 2019 at http://www.skindivinghistory.com/mfg_retailers/f/Florida_Frogman/19.html.
60. ^Early Mfg. & Retailers - US Divers No.43. Retrieved on 26 February 2019 at http://www.skindivinghistory.com/mfg_retailers/u/US_Divers/43.html.
61. ^US Patent US2815751: Breathing valve for a submarine mask. Retrieved on 27 February 2019 at https://patentimages.storage.googleapis.com/59/03/10/480531a12da43d/US2815751.pdf.
62. ^https://www.letsgotomaui.net/da-kine/full-face-snorkel-mask-dangers/
63. ^https://www.cbsnews.com/news/hawaii-full-face-snorkel-mask-related-deaths/
64. ^ ^abNOAA Diving Program (U.S.) (December 1979). '4 - Diving equipment'. In Miller, James W. (ed.). NOAA Diving Manual, Diving for Science and Technology (2nd ed.). Silver Spring, Maryland: US Department of Commerce: National Oceanic and Atmospheric Administration, Office of Ocean Engineering. p. 24.
65. ^Gayle Jennings (2 April 2007). Water-Based Tourism, Sport, Leisure, and Recreation Experiences. Routledge. pp. 130–. ISBN978-1-136-34928-7.
66. ^Fodor's (1988). Fodor's 89 Cancun, Cozumel, Merida, the Yucatan. Fodor's Travel Publications. ISBN978-0-679-01610-6.
67. ^Staff. 'Snorkeling Safety'. Retrieved 5 January 2017.
68. ^The 5 Commandments of Snorkeling Etiquette, 2015
69. ^Bourjon, Philippe; Ducarme, Frédéric; Quod, Jean-Pascal; Sweet, Michael (2018). 'Involving recreational snorkelers in inventory improvement or creation: a case study in the Indian Ocean'. Cahiers de Biologie Marine. 59: 451–460. doi:10.21411/CBM.A.B05FC714.

Sources[edit]

• The British Sub-Aqua Club; Holbrook, Mike (2001). Snorkelling for all. London: Ebury. ISBN978-0091883041.

External links[edit]

• National Parks Conservation Association page on snorkeling. Archived from the original
• US patent 1901219, Joseph L. Belcher, 'Breathing apparatus', issued July 30, 1932. Earliest known patent for snorkel.

Doing It Right (DIR) is a holistic approach to scuba diving that encompasses several essential elements, including fundamental diving skills, teamwork, physical fitness, and streamlined and minimalistic equipment configurations. DIR proponents maintain that through these elements, safety is improved by standardizing equipment configuration and dive-team procedures for preventing and dealing with emergencies.^[1]

DIR evolved out of the efforts of divers involved in the Woodville Karst Plain Project (WKPP) during the 1990s, who were seeking ways of reducing the fatality rate in those cave systems. The DIR philosophy is now used as a basis for teaching scuba diving from entry-level to technical and cave qualifications by several organizations, such as Global Underwater Explorers (GUE),^[2]Unified Team Diving (UTD)^[3] and InnerSpace Explorers (ISE).

• 2Tenets
  • 2.3Equipment
  • 2.5Preparation
    • 2.5.2Dive planning
• 4Equipment and configuration
  • 4.4Regulators
    • 4.4.5Regulator configuration
  • 4.5Cylinders
  • 4.10Dive lights
• 6DIR criticisms and controversies
• 7Comparisons between DIR and other recreational and technical diving groups

History[edit]

The DIR approach (and name) evolved out of the Woodville Karst Plain Project (WKPP) in the mid-1990s, where the objective was conducting dives in a very high risk environment: Not only cave diving, but also deep, long duration and exploration of previously unknown parts of a very large cave system. The origins of the approach to equipment taken by DIR practitioners can be found in the 'Hogarthian' equipment configuration attributed to William Hogarth Main.^[4] These individuals, along with many others, were attempting to develop equipment and procedures to allow the safer exploration of the deep submerged caves in the area. Successfully carrying out the advanced diving required for deep cave penetration, as in the Woodville Karst Plain Project, places a great need to focus on the fundamentals of exactly how such diving should be carried out, and how equipment should be selected and configured for this type of diving, to maximise mission effectiveness and minimise risk. The DIR approach was originally confined to cave diving, but soon spread to other forms of technical diving.^{[citation needed]} Since recreational diving is the natural source of future technical divers, the DIR philosophy was extended into this field, although the recreational practices were already considered acceptably low risk by most diver certification agencies and insurance companies.^{[citation needed]}

The phrase 'Doing It Right' as applied to diving is thought to have appeared in 1995 in an article by George Irvine III.^[5] Irvine and Jarrod Jablonski eventually formalized and popularized this approach as DIR, promoting its practices for all forms of scuba diving. Irvine's polemic style and inflexible stance led to a great deal of controversy and, while popularizing the style among some people, repelled many others.^[6] This has begun to ameliorate somewhat. As of 2009, there are at least two US-based dive training organizations, Global Underwater Explorers (GUE) and Unified Team Diving (UTD), and many independent dive instructors who teach a DIR style of diving. GUE renamed its 'DIR Fundamentals' course to 'GUE Fundamentals' in 2007, distancing itself somewhat from the acronym 'DIR'.^[2] UTD have modified the original DIR methodology to suit sidemount and Closed circuit rebreather use.^{[citation needed]}

Tenets[edit]

Doing It Right is about diving safely for personal enjoyment of the underwater environment^[7] The principle of buddy support and teamwork using basic, well practiced, familiar and standardised safety procedures is central to the philosophy. Use of simple, reliable, well matched and rugged equipment that is versatile in its application, and familiar to all team members is seen as the logical way to achieve the highest levels of teamwork and as a means of minimizing task loading on the divers by reducing drag, and allowing good trim and buoyancy control, maneuverability and freedom of movement and low risk of entanglement. The familiar DIR equipment configuration is a means to this end.^[8]

A holistic approach to diving is a central DIR principle.^[9] DIR is a system and as such equipment configuration should be considered within the context of the whole philosophy, and the ultimate aims of ensuring safety, efficiency and enjoyment.^[9] Diving equipment is viewed as only one part of the diving activity. DIR proponents believe that the most important piece of dive equipment is the diver, followed by the team, and the interactions between the team members.^[8]

Experience[edit]

Experience is considered a key aspect of becoming a good diver. It is the result of training and familiarity with the demands of the various environments. Training of fundamental skills by a suitably competent professional educator is recommended as the most effective route to gaining experience safely, however this is not a substitute for time spent in the water practicing and using the skills, as this produces the familiarity and comfort of repetitive exposure,^[10] eventually allowing the diver to perform the skills with minimised stress and delay, even in difficult circumstances.

Ability[edit]

Competence is a combination of knowledge, aptitude and practice of good technique. Knowledge and technique can be learned, and assiduous practice can compensate for lack of natural aptitude. Course training does not generally provide sufficient time to hone skills and develop the optimum level of knowledge, and therefore additional review and practice are usually necessary.^[11]

Equipment[edit]

DIR proponents say equipment configuration should be simple, streamlined, exactly sufficient or minimalistic and applicable to all diving situations, from shallow reef diving to long cave penetrations.^[2] It must also be appropriate for reliable team support, so the configuration of each diver's equipment must be familiar to all members of the dive team^[8]

Streamlined equipment and standardised configuration[edit]

The standard DIR equipment configuration is fairly well established.^[12]The configuration has been designed and evolved to work in all situations. The intention was to improve a diver's efficiency and overall convenience and minimise risk. The configuration is minimalist and streamlined, and equipment should not hang free, stick out or increase drag unnecessarily, or cause entanglement.^[2]

Balance and trim[edit]

The DIR rig is carefully weighted to ensure that the diver is not overweight but is able to maintain accurate depth and trim at any decompression stop. This requires assessment of how each component part fits into and affects the buoyancy characteristics of the configuration as a whole.^[2] The choice of cylinder size and material must be chosen with due consideration of the effects on buoyancy and trim in conjunction with the selection of dive suit^[8]

Gas selection parameters[edit]

The parameters for gas use recommended by DIR are relatively conservative.^[2] These include:

• Equivalent narcotic depth (END) of less than 100 fsw (30 msw)
• Partial pressure of oxygen (pO₂) not exceeding 1.2 atm (1.2 bar) for the active sectors of a dive. Currently 1.0 atm.^{[citation needed]}
• Partial pressure of oxygen (pO₂) not exceeding 1.4 atm (1.4 bar) for decompression stops, 1.6 atm for 100% oxygen (may be exceeded in dry chamber).
• Liberal use of helium together with the conservative use of oxygen to limit the toxic effects of oxygen, nitrogen and carbon dioxide. Air is not listed as one of the recommended gases: Either nitrox or trimix will have advantages over air at any given stage of a complex dive.
• Standardised breathing gases are promoted to simplify the logistics of mixing gases and marking cylinders. This makes decompression planning simpler and reduces task loading when sharing gas in an emergency, as all divers in the team have the same decompression plan.
• Cylinders are marked only with the maximum operating depth (MOD) in a clear and easily identifiable manner. This practice is used in conjunction with standardised mixtures as a simple and reliable identification procedure.^[2]

Unified team[edit]

The notion of a unified dive team is central to the DIR philosophy. A unified team acts in concert to preserve the safety of the team and meet the goals of the dive. All of the team's equipment and its consumables (i.e. breathing gas, batteries) are held in common and dedicated to the safety, comfort and dive goals of the team.^{[citation needed]} In addition, each team member should be familiar with what all other team members are carrying.^[13]

Divers of similar competence and preparation are grouped together to form a team that provides greater safety than possible if they dive independently. By maintaining a similar high level of care and attention among the team members, the experience of diving as part of the team can be more rewarding and satisfactory than diving without the support of such a team.^[2]

Preparation[edit]

The notion of preparation within the DIR ethos applies well before the divers approach the water. It encompasses personal physical fitness, mental fitness, rigorous planning and pre-dive safety drills and routines.^[14]

Fitness[edit]

DIR divers are expected to keep themselves physically fit, as this reduces the stressful effects of high levels of exertion, and provides the diver with a better chance of effectively dealing with a problem. GUE minimum level of fitness is equivalent to a 400m continuous swim. with a medium fitness rated as 1600m continuous swim.^[15] Whilst all forms of diver training promote physical fitness, the DIR approach takes it further than most.^{[citation needed]}

Mental fitness includes focus on the dive, so that the diver can be responsive to the demands of the dive and remain aware of the situation and surroundings, and respond timeously to contingencies, so that development of crises can be curtailed at an early stage.^[16] This approach is supported by the findings of Blumenberg (1996)^[17] and Lock (2011)^[18]

Dive planning[edit]

Unique features[edit]

Several features of the DIR approach are at odds with more conventional forms of diver training.

• Ratio decompression — In addition to using established algorithms for decompression diving, DIR utilizes ratio decompression, which is assumed to yield results that are always on the 'safe' side^{[citation needed]} of the Bühlmann decompression algorithm and the Varying Permeability Model. RD is based on the common patterns of output from decompression programs that can be closely approximated by simple calculations in the diver's head. Because no dive computers use this methodology (and DIR eschews dive computers in any event), divers are taught to recalculate decompression schedules on the fly (although they still plan their dives in advance). The degree to which RD is used varies; UTD depends on it heavily, and GUE teaches it as a backup method.^{[citation needed]}

Training[edit]

DIR training differs from mainstream Rec/Tec in several ways.

Agencies that promote DIR do not train divers younger than 16 (UTD),^[19] (GUE Rec 1),^[20] or 14 for divers certified by another agency (GUE Primer),.^[21]

There are several standardised procedures and safety drills developed by the DIR community. These include:

• Breathing the primary—The primary regulator used during the dive for breathing the back gas is the long hose on the right cylinder valve. The secondary/backup regulator is on the left cylinder valve and is held under the chin on an elastic 'necklace'
• Bubble check—to ensure there are no leaks or before committing to the dive. Divers check each other's equipment for bubbles indicating leaks. specifically around first stages, second stages, and gas hoses and fittings and make a general visual check that everything is in place.
• S-Drill—short for safety drill—is a simulated donation of the long hose to ensure that it deploys freely and is routed correctly.
  • In a modified S-drill the long hose is deployed before entering the water or whilst on the surface of the water to make sure it is free.
  • In a full S-Drill the divers descend a few metres and perform simulated out of gas exercises so that they all get practice at sharing gas.
• Valve Drill—to make sure the back gas cylinder and manifold valves are fully open and that the diver can open and close them.
  • In a modified valve drill the diver reaches back and checks that the valves are fully open.
  • In a full valve drill the valves are closed and re-opened in sequence and the regulators checked while a team member stands by in case of problems.

Fundamental diving skills[edit]

DIR holds that lack of basic diving skills is common in recreational and technical diving, and the lack of these skills results in stress, fatigue and occasionally fatalities. Poor technique is said to increase stress, and reduce ability to cope with emergencies, which often develop as an accumulation of poor technique and lack of situational awareness. Skill levels should be appropriate to the environment, planned dive profile and tasks.^[22]

Unlike some other diver training and certification agencies, GUE is specific about the required standard of performance for the basic skills for a new diver, an advanced diver, and an advanced technical diver, and specifies the equipment the diver should be carrying during assessment in the latter case.^[23] This allows an objective assessment of skills. The diver and instructor can both agree whether the skill has been performed as required, and the diver has a specific goal to aim for while practicing. These criteria are shared by professional diver training quality assurance organisations.^[24]

The DIR view is that it is essential that divers master the skills of mask clearing, even if it takes many repetitions, as inability to adequately clear the mask leads to stress and distraction, and the dislodging of the mask during a stressful stage of a dive may then lead to panic.^[25]

Buoyancy control is considered both an essential skill and one of the most difficult for the novice to master. Lack of proper buoyancy control is likely to disturb or damage the surroundings, and is a source of additional and unnecessary physical effort to maintain precise depth, which also increases stress.^[26]

Trim is the diver's attitude in the water, in terms of balance and alignment with the direction of motion. Accurately controlled trim reduces swimming effort, as it reduces the sectional area of the diver passing through the water. A slight head down trim is recommended to reduce downthrust during finning, and this reduces silting and fin impact with the bottom. Buoyancy compensators and weighting systems that make horizontal trim difficult are deprecated for this reason. Systems are recommended that concentrate weight centrally and restrict weighting to what is actually needed to compensate for equipment buoyancy and use of gas during the dive.^[27]

The DIR diver must be aware of remaining gas supply at all times, as this is the critical requirement for survival. The diver must be aware of how much gas is needed to return to the surface from any point in the dive, and ensure that this, and a suitable safety margin, is available according to the dive plan.^[28]

Efficient propulsion is not only necessary for good gas endurance, but also for skilled maneuvering. The diver is required to master finning styles that are suitable for the different environments and circumstances, and fins must not only be suitable for performing the required finning techniques, but must provide sufficient thrust when needed, and minimise snagging on lines and other items. Overly flexible fins, hinged fins and split fins may be unable to provide these requirements, and are therefore considered an unacceptable handicap. Straps must not fail, and simple, snag free and reliable systems are required.^[29]

The ability to find one's way around during a dive can be critical to survival. Navigation skills and techniques appropriate to the environment must be mastered. The dive plan must be understood and followed, and contingency plans should be available for the foreseeable deviations from the plan.^[30]

DIR divers must be completely dedicated to the buddy system, primarily in the interest of safety, but also because failure to follow the expected procedures is likely to compromise the dive plan. The DIR buddy and his/her equipment are regarded as backup to the whole team, and provide necessary redundancy in case of equipment failure or other accident, without overburdening the divers with additional equipment.^[31] Communication is central to buddy and team diving. DIR divers must be competent at underwater communication by hand signals and light signals, and to use them to ensure that they are always aware of the status of the rest of the team. DIR divers have an extended range of hand signals, some particularly relevant to overhead and decompression diving. Divers are expected to understand hand signals by touch in case of zero visibility.^[32]

Familiarity and comfort with equipment are considered important, as the diver should be able to perform necessary procedures quickly and effectively both for efficiency in normal diving, and for safety in emergencies, where any delay can increase the risk of escalation. The use of standardised equipment configurations and procedures is promoted as conducive to familiarity and thereby comfort. The recommended configurations are claimed to be optimised for both comfort and efficiency. DIR proponents indicate that poor equipment handling skills are often due to shortcomings in training programmes, but can also be a result of inherently sub-optimal configurations.^[33]

DIR proponents consider that rescue skills and training are necessary for all levels of diver, not only to perform a rescue in an emergency, but also because the training and skills are likely to reduce the risk of an emergency developing in the first place. Most emergencies are the result of bad planning, inadequate skills and lack of awareness culminating in a situation beyond the control of the diver. Self rescue occurs when the diver pre-empts the development of the emergency by recognising the early stages and taking appropriate action. This is facilitated by the same training appropriate to rescue of another diver. The second way of preventing an emergency is monitoring by an aware and alert buddy, who may pick up signs of impending problems by situational awareness and skilled observation, one of the advantages of the unified team concept and effective communications within the team. Actual rescue, though desirable when necessary, often indicates a failure to manage minor problems and a lack of attention to signs of stress buildup.^[34] However, there are also occasions when things do go wrong in spite of good planning and procedures—and good training and well honed skills contribute to a successful rescue effort,^[17] rather than a double fatality.

The factors most likely to increase risk of an accident are considered to be:^[35]

• Going beyond one's level of training. This can be mitigated by appropriate further training.
• Going beyond one's personal level of comfort. This can be mitigated by working up towards dives outside of the current comfort zone in stages. Familiarity and practice reduces stress and improves awareness of detail. Maintaining an adequate standard of fitness can make a big difference to comfort.
• Diving beyond the range of application of a gas mixture. Gas mixtures must be used that are suited to the dive, and it must be possible to positively identify the range of application for the mixture in use. Clear labeling of maximum operating depth is the most effective way of marking the cylinder. Opening the cylinder valve only after checking the MOD and testing the regulator is a positive method for ensuring that the correct gas is in use. Restricting END to 100 feet (30 m) minimises the risk of nitrogen narcosis contributing to poor judgement and reduced efficiency. Stress on the diver can be caused by a large range of factors. It is not possible to eliminate them all, but a large number may be reduced by appropriate training, adequate skills and fitness, the use of suitable equipment in effective configurations, and effective teamwork and communications. In effect, this is the purpose of the DIR system.

Equipment and configuration[edit]

DIR equipment choice and equipment configuration should be considered together, as the two are philosophically inseparable. A change to one item of equipment may have complex consequences for the entire configuration and for procedures that depend on that equipment configuration. These consequences must be analysed before making a change. This is not to say that DIR equipment and configuration is immutable and can not be improved, but that all the consequences to the system must be considered when a variation is contemplated, so that knock-on effects can be avoided.

The basic principle of DIR diving also includes familiarity of all divers in the team with all equipment used by the team, and all the procedures intended to be used by the team, and that interchangeability of DIR divers between teams is highly desirable. The natural consequence is that changes are not easily accepted unless very well motivated. This may be interpreted as inflexibility by persons who do not analyse the philosophy of the system.^[1]

When there is a choice between two items of equipment with the same purpose, and one is clearly better than the other for a reason that affects risk and safety, the DIR philosophy insists that only use of the safer item is doing it right.

The configurations and procedures recommended by the DIR proponents did not spring into existence fully formed and perfect, they were developed, largely by trial and error, and significantly by William Hogarth Main, who continues experimenting with configurations and equipment in the interests of improving the system.

The DIR equipment system can be described as minimalist. Items of equipment that do not serve a useful purpose on a dive are considered a liability. Redundancy is provided where necessary within the personal equipment of the diver, and where possible by availability of team equipment. Multiple redundancy across personal and team equipment is only resorted to when necessary.

Streamlining and maintaining a low profile and cross sectional area are important considerations but effectiveness and robust applicability to a wide range of environments are possibly more important, as they allow a basic core configuration that is effective in virtually any recreational diving situation, and allow standardisation of procedures, which in turn lets the diving team be assembled from similarly trained and equipped divers, who integrate more easily into an effective team. In this context, streamlining includes the aspect of reducing hydrodynamic drag when swimming, but more importantly, the reduction of entanglement and entrapment hazards due to equipment components to a minimum.

This philosophy does not preclude the use of equipment that is necessary for a special task, but would be applied to the choice of the equipment and how it is transported and deployed.

Backplate[edit]

The backplate and harness forms the foundation of the DIR diving equipment system. The back plate is used to support the buoyancy compensator and back gas cylinders and provides storage for other items. The back plate is a rigid plate with minimal padding ^[36] bent from flat stainless steel ^[37] or aluminum ^[38] plate and slotted for straps, or formed from other materials with similar rigidity characteristics. The choice of materials is determined by the operational needs of the diver and the environment. The back plate is designed primarily for double tanks and adaptable for singles tanks as required, using either an adapter ^[39] or strap cutouts.^[40]

Harness[edit]

The harness supports the backplate and its cargo on the diver. It is formed from one continuous length of 2-inch (5.1 cm) nylon webbing secured through dedicated top and bottom slots in the back plate.^{[41][42][43][44]} The webbing must be adjustable and is secured with a single stainless steel buckle located on the diver’s right waist,^[45] this position lessens the potential of accidental opening by the crotch strap.^[42] A crotch strap runs from the bottom of the back plate to a loop in front that the waist strap passes through, securing the harness/back plate system to the diver. The crotch strap prevents the harness system from shifting and riding high on the diver. The harness supports 5 “D” rings, one placed on the divers left waist, one on each shoulder strap, and two on the crotch strap.^[42] The left side waist “D” ring is used to attach the back gas SPG, stage bottles, and other gear that may be required for a particular dive.^[46] The shoulder “D” rings are used for securing the backup lights, the primary regulator when not in use, and temporary storage of other pieces of equipment.^[47] The front crotch strap “D” ring is to be used solely for attachment to a DPV (scooter), and the rear “D” ring is used for attaching equipment as needed.^[42] The primary light battery canister is placed on the waist belt on the right, secured with a secondary stainless steel belt buckle or the primary belt buckle as best suits the size of canister and diver.^[43]

Buoyancy control[edit]

Buoyancy control involves the balance between the buoyancy of the various items of equipment during the course of a dive. The main variables are:

• Suit buoyancy, which is usually significantly positive, and may vary with depth
• Cylinder buoyancy, which can vary from significantly negative to slightly positive, and increases during the dive as breathing gas is consumed
• Harness and accessories, which are usually all slightly to significantly negative
• Ballast weights, which are a constant negative
• Buoyancy compensator, which is adjustably positive, and compensates for the combined effect of the other equipment.

In keeping with the minimalist philosophy, buoyancy compensators should be only as large as is necessary to provide neutral buoyancy at any point in the dive, and should allow easy, confident and reliable dumping. The volume should not exceed about 65 pounds (29 kg) for twin cylinders or 30 pounds (14 kg) for single cylinders, on the premise that needing more would be evidence that the rig is unbalanced and unsafe, as the diver should be able to drop excess weight and swim up without a functioning buoyancy compensator. An unnecessarily large bladder volume is considered dangerous as it can contribute to a runaway ascent. Wings with the expansion constrained by elastic cords are also deprecated as they can trap air pockets, making it difficult to get all the air out.^[48]

Dual bladder buoyancy compensators are considered both unnecessary and unsafe. Unnecessary in that there are alternative methods available to a correctly rigged diver to compensate for a defective BC, and unsafe in that there is no obvious way to tell which bladder is holding air, and a leak into the secondary bladder may go unnoticed until the buoyancy has increased to the extent that the diver is unable to stop the ascent, while struggling to empty the air from the wrong bladder. Monitoring the air content of two bladders is unnecessary additional task loading, which distracts attention from other matters.^[49]

The corrugated hose of the inflator assembly should be long enough to easily dump air from the bladder and no longer, as unnecessary length makes it difficult to streamline.^[48] The inflator mechanism must not be a high flow type as these use a non-standard connector, and can fill the wing dangerously quickly if the valve sticks open. It is easier to deal with a runaway inflation on a low flow rate inflator.^[50][48] A pull dump valve on the inflation manifold is an unnecessary additional point of failure.^[48]

The drysuit is considered unsuitable as the default method for compensating for weight changes due to gas consumption during the dive. Excessive volume in the suit has an undesirable effect on trim, the suit provides poor support for the back gas cylinders compared to a wing, where the buoyancy is arranged where it is needed and dumping gas in an emergency is easier from the wing as a wing can dump in the inverted (feet up) position.^[48]

Regulators[edit]

Connection[edit]

The yoke connector is vulnerable to blowing the O-ring seal when impacted against an overhead or other obstacle. As the loss of the o-ring that seals the first stage to the cylinder valve causes a major loss of breathing gas, this weakness of the yoke connector is unacceptable, considering that the alternative DIN connection is freely available and more resistant to loss of seal on impact. The DIN connection also has a slightly lower profile in the vulnerable manifold area and is therefore less likely to be impacted in the first place, particularly with normal outlets (outlets that are perpendicular to the cylinder axis, as opposed to those tilted at about 45°).^{[citation needed]}

First stage[edit]

Second stage[edit]

Hoses[edit]

The long hose(5 to 7 ft, depending on diver height) is required in overhead and decompression diving as it simplifies air sharing, thus reducing risk. It is always mounted to the right cylinder valve post, as the right cylinder valve is unlikely to be rolled closed by contact with an overhead surface, and possibly jammed in this position.^[51] It is optional in shallow, open water diving where there is direct access to the surface and no requirement to travel any considerable distance while sharing gas.^[52]

The secondary regulator hose length should be no longer than necessary to breathe comfortably and move the head normally, so that it is less likely to snag.^[53]

Regulator configuration[edit]

Two first stages are used when twin cylinders are used, or when a 'Y' or 'H' cylinder valve is used. A long hose is used for the primary, which is mounted on the right cylinder valve or right post of the 'Y' or 'H' valve. The right side first stage also supplies gas for the BC inflation hose, as this side is at a lower risk for roll-off. The left cylinder first stage supplies the backup second stage, which is routed over the right shoulder and stored on a necklace, the suit inflation hose, and the submersible pressure gauge. The SPG hose is routed down the left side of the harness and the SPG is clipped to the left hip D-ring.^[51]

When diving with a single first stage on a single cylinder, both second stage hoses route to the right, and the inflator hose and SPG hose route to the left. This lets divers use all the components in exactly the same way and store them in the same places as when they use two first stages. A long hose may be used for the primary, but is not obligatory for shallow open water diving.^[54]

Stage regulators[edit]

Stage regulators are fitted with a submersible pressure gauge on a short (6 inches (150 mm)) hose, bent so the diver can read it easily, and held in place against the cylinder valve or first stage with bungie cord. The regulator hose is octopus length (about 1 metre (39 in)) and when not in use is secured to the cylinder under an elastic band. The cylinder valve is closed when not in use, though the regulator may be pressurised to keep water out before starting the dive.^[55]

Submersible pressure gauges[edit]

The SPG must be neatly clipped off where it cannot snag or cause unnecessary drag. This implies a hose just long enough to reach the waist belt D-ring on the left hip, where it is clipped, and no additional instruments in a console to increase bulk. The gauge is read by unclipping with the left hand, and bringing it up to where it can be read without disturbing the trim and progress of the diver, whether finning or using a DPV.^[53]

Cylinders[edit]

Cylinder boots may snag on wreckage or tight restrictions in a cave, and retain water, encouraging rusting of the bottom of the cylinder. In squeezing through narrow places, the cylinder boot and other things fastened to the side of the cylinder may snag on the surroundings. Netting around cylinders can catch on obstructions. As they are not necessary they are deprecated.^[56]

Cylinder valves and manifolds[edit]

Barrel sealed manifolds with two O-rings in parallel are more tolerant of minor misalignment and varied centre distance than face-sealed manifolds with single O-ring seals which are more likely to leak if impacted.^[57] Isolation manifolds provide the possibility of closing off one cylinder if there is an unrecoverable leak, conserving the remaining gas in the other cylinder. Cylinder or manifold valve knob extension operators (slobwinders) can be stiff, can trail and snag on things, and can be difficult to find when needed.^[48] Valve- and manifold protector frames are not normally necessary and may be worse line-traps than the valves. Some models make it more difficult to reach the valve, and some can increase the diver's profile.^[58]

The knobs fitted to cylinder valves and manifolds should be able to withstand a moderate impact without fracturing or bending the spindle and jamming. The approved valve knob is hard rubber or non-brittle plastic, which flexes to absorb much of the impact energy, with a metal insert, so the connection to the spindle is less likely to strip. Spring loading of the valve knob can also absorb impact loads, but only from some directions. Hard plastic and metal knobs are not approved. Hard plastic knobs may be brittle and break under impact, and metal knobs are more likely to transfer the full impact to the spindle, thus a greater risk of bending or shearing the spindle and rendering the valve inoperable. If the valve is rolled off (closed by friction against the environment) at the same time, the gas supply is isolated and unavailable to the diver. ^[59] Almost all knobs are currently (2018) made of hard rubber or non-brittle plastic.

It is possible to accidentally turn off an isolation valve during a fill or a safety drill, and a closed isolator can cause problems. The isolator is normally left completely open, so the manifolded cylinders maintain equal pressure during filling and use, and are closed during an emergency to prevent gas loss from both cylinders, during safety drills, or to identify a fault. Symptoms of a closed isolator depend on which tank the diver is breathing from. If the gauge is on the same tank that the diver is breathing from, the diver may notice an unusually quick reduction in pressure, and mistakenly believe that they are running out of gas. If the gauge and regulator in use are on separated by the isolator, the gauge will continue to read the same pressure as the other tank is depleted. When the cylinder in use is emptied, the gauge will still read full, and the diver may assume that the regulator has malfunctioned. This is only likely to happen to divers that are paying little attention to their gas supply, as an apparently abnormally fast or slow depletion of gas supply is an indication that valve status should be checked, and if necessary, corrected.^[60]

Back cylinders[edit]

Stage and decompression cylinders[edit]

A stage cylinder contains gas intended to extend bottom time. A decompression cylinder contains gas intended for use during decompression, usually a different mixture to the bottom gas. Externally the equipment is basically identical, except for the marking identifying the contents by maximum operating depth.

The DIR requirement for stage and decompression cylinders for the dive is that they should be aluminium, for reasons of near-neutral buoyancy. The cylinders should be rigged with stainless steel bolt snaps of a size to allow easy operation. If gloves are worn in cold water, a large snap is needed. The snaps must be attached to a line clamped about halfway along the cylinder. The upper snap is attached to the line near the neck and close to the tank, and the lower snap to the line that extends beyond the clamp. ¼' braided line and stainless steel hose clamps are standard. The distance between the snaps should be about 16' to match the distance between the D-rings from which it will be suspended.

The cylinder is carried clipped to the shoulder and hip D-rings on the left side, and should be held close at the shoulder and relatively loose at the hip, to allow it to find a streamlined position at the diver's side. It must be possible to cut the cylinder free if the snaps should jam. Each cylinder must be marked with Maximum Operating Depth on both sides where it can be seen by the diver and others in the team. Other markings are considered extraneous.^[61]

Mask[edit]

Low volume masks are used as they reduce drag and are easier to clear. A spare mask is recommended if the dive will be long with extended decompression.^[53]

Snorkel[edit]

The snorkel is an adjunct to diving without breathing apparatus and face-down surface swimming. In overhead diving they are considered a significant entanglement hazard and are not worn on the mask strap while underwater, as this could interfere with deployment of the long hose in an emergency.^[62]

Fins[edit]

Stiff bladed fins with spring straps replacing the original plastic buckles and rubber straps are recommended. Short, stiff blades are suitable for reverse kick and other kick styles necessary for maneuvering in a tight overhead environment and can generate adequate thrust provided the diver has sufficient leg strength. The spring straps are considered more secure and reliable than the conventional rubber and plastic straps. All aspects of fin design and construction should minimize the risk of entanglement or breakage.^[63][48]

Knife or cutting tool[edit]

The knife is carried in an open sheath^{[clarification needed]} on the waist belt to the left of the crotch strap where it can be reached by either hand and is unlikely to snag. It is a line cutting tool and does not need to be large or to have a point, but must have a sharp edge that is effective on thin lines and nets.^[46] Paramedic shears and purpose designed line cutters can be kept in a wetsuit/ drysuit pocket if there is a high risk of entanglement.^[48]

Dive lights[edit]

The basic DIR configuration includes a single primary canister light at the diver's right hip and two reserve lights clipped to the chest D-rings and secured against the harness straps by rubber bands. Lights are optional for shallow open water diving.^[64]

Primary light[edit]

The recommended primary light is a canister light with a Goodman handle light head. The Goodman handle allows the diver to direct the beam of the light while leaving the hand free to perform other functions. The principle of only carrying equipment that is necessary would make the primary light a requirement on dives where a light is needed, but not otherwise. However even in good visibility a powerful light can enhance the dive by restoring full colour at depth. The canister is carried on the waist belt to the right side, secured by a belt buckle, and the light head is carried on the left hand when in use, and clipped to the right shoulder D-ring when not in use or when the hands are needed to perform an operation where the light would be in the way. The primary light would be optional on well illuminated recreational dives.^[65]

Backup lights[edit]

Backup (reserve) lights are carried where they are unlikely to snag, and cause minimal drag, but can be reached and operated by one hand. Two are required for overhead diving. The storage position for backup lights is clipped to the chest D-rings and held against the harness by rubber bands, where they are tucked away and unlikely to snag, but remain easily accessible to both hands, and can be turned on before unclipping, so they can be easily found if dropped. Fresh non-rechargeable batteries should be installed before any dive where burn time of the backup light may be critical to safety, and burn time should allow exit from any point in the dive with a margin for problems.^[66]

Scooters[edit]

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The “tow behind” scooter arrangement is preferred to the ride-on style scooter which creates higher drag as the scooter and diver stacked together present a greater cross sectional area to the water than when one follows the other, and they make it more difficult to tow another diver or additional gear. The tow behind scooter reduces these problems as the diver is towed in the wake of the scooter, the propeller is visible and in front of towed equipment, and they are more easily steered, particularly in tight spaces. Scooter tow lanyards run from the scooter handles and clip on to the front crotch strap D-ring when in use, to pull the diver by the D-ring, taking most of the load off the arms, and allowing control with one hand. The most efficient position for the scooter is at a relaxed arm's length in front, offset below so the propeller wash will not hit the diver.^[60]

Depth Gauge[edit]

Depth gauges need to be viewable at all times, particularly during ascent and decompression. They are wrist-mounted on the right arm, to allow monitoring while buoyancy is being controlled using the left hand to operate the inflator hose and dump valves on the left. They should not be mounted on a bulky console and dragged behind the diver, as this could damage the environment on contact, or increase the risk of entanglement, and require retrieval of the console every time the depth is to be checked.^[60]

Compass[edit]

The compass is mounted on the wrist, as the alternative mounting on a retractor or on a console are considered more likely to snag or drag on the bottom, thereby potentially damaging delicate structures and organisms.^{[citation needed]} It is worn on the left to keep it away from the magnetic field of the scooter motor when a scooter is used.^{[citation needed]}

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Variation to suit the environment[edit]

When the DIR equipment configuration is used in different environments, equipment details change to suit without compromising the basic concepts.^[67]

• In cold water, dry suits, hoods, gloves are substituted for or added to wet suits
• Overhead (cave or wreck penetration) diving requires additional lights (total of 1 primary, 2 backups)
• Shallow open water allows single cylinder and smaller volume buoyancy compensator, Primary hose length may be reduced as there is no requirement for single file transit through small spaces.
• A decompression buoy is carried when there is a reasonable chance that it may be useful.
• The Diver Life Raft and Surf Shuttle are inflatable safety devices for diving where currents or distance could create a life-threatening situation if the diver is separated from the dive boat. They are intended as flotation aids for lost dvers or those facing long surface swims.^[68] These items can be stored in a pocket mounted to the diver's backplate.^{[citation needed]}

'Doing It Wrongly'[edit]

Some DIR divers refer to non-DIR diving practices as DIW (Doing It Wrongly), and the non-DIR-compliant divers as 'strokes'. The website frogkick.nl^[69] claims to represent the DIR philosophy and expresses an opinion that the practices and equipment are 'faulty'. This is a highly controversial matter in recreational and technical diving. Some of the tenets are logical, supported by evidence and may even be undisputed. Others are strongly disputed, and may lack robust evidence for the claims, or may be defended by inconsistent logic. Others again may be more applicable to specific aspects of technical diving, and not generally best possible practice:

The following listed practices and equipment are some of those deprecated by persons representing themselves as DIR divers and/or training organisations:^[70]

• Badly designed clips, which may rust, or have sharp edges, or may open and break the connection unintentionally, potentially losing equipment, and particularly clips that may snag a line and clip themselves on without the intention of the diver and are colloquially known as suicide clips.^[71]
• Decompression computers are recognised as being useful but are not a substitute for planning decompression and gas requirements of a multi-level profile before the dive. Electronics may fail and batteries may run out.^[48]
• Instruments mounted in a console attached to the pressure gauge, supported by the high-pressure hose are vulnerable to snagging and impact with the environment, and reaching for the console to red the instruments occupies a hand, increasing task loading. Depth and time instruments should be worn on the wrists where they can be monitored constantly during ascent without occupying a hand.^[48]
• Helmets for head protection, and head mounted lights may snag the long regulator hose which is looped around the neck and may cause difficulty changing the diving mask.^[48] Head mounted lights also increase diver profile and hydrodynamic drag, and increase the risk of shining the light in the buddy's eyes when looking towards him.^[48] They are difficult to use effectively for signalling purposes.
• Negatively buoyant steel stage cylinders can cause trim problems and buoyancy difficulty if handed off.^[48]
• A battery canister for the primary light carried at the lower end of the back cylinders (butt mount) may interfere with the diver's leg action in finning, isnot as easily reached while diving, and needs a longer lamp lead, which is more vulnerable to snagging behind the diver.^[48] If the canister floods, the diver's trim is may be adversely affected (feet down), and it is more difficult to remove the canister during the dive if necessary^[43]
• A gas switch block increases the risk of a diver unintentionally switching or being switched to a breathing gas unsuited to the depth, with possibly fatal consequences, and compromising the decompression plan.^[72]
• All-metal connections cannot be cut free in an emergency if the connector jams.^[48]
• Non-standard gas connections for demand valve hoses and inflator hoses for dry suits and buoyancy compensators conflict with the requirement for all team members' gas connections to be the same, so that they can be shared in an emergency.^[48]
• Swivelling gas connections are an additional point of possible failure and are not needed with DIR hose routing.^[48]
• A Snorkel is undesirable when it has no meaningful benefit, and its presence is an additional hazard if it can snag on something. If on the head, it may snag on something and pull the mask off. If on the leg, it could snag the weight belt when ditched in an emergency, or snag on nets or lines.^[48] GUE policy has moved away from this, and while noting that a snorkel is only useful at the surface and can be a snagging hazard underwater, recommends that snorkels be plain, simple and unadorned with gimmickry, and that the diver should learn proper snorkeling technique.^[60]
• Buoyancy compensator inflation control devices with an integrated secondary demand valve^[48]
• A small writing slate on a wrist does not have much space for writing and clutters the arm. A 'wet-notes' pad carried in a pocket is the recommended alternative.^[48]
• A pony bottle mounted on the back cylinder is deprecated as it is easier to confuse which demand valve is connected to which cylinder. This could lead to the diver accidentally choosing the wrong gas for the depth if the contents are decompression gas.^[7]

Variations and schisms within DIR[edit]

However, as with all great movements, comes inevitable corruption and fragmentation. Today, DIR has spread to every corner of the globe, with self-appointed DIR groups emerging in dozens of different countries. Given their physical separation, their lack of centralized direction, their own specific agendas, beliefs, power struggles and constraints, these satellite groups cannot help but to promote a version of DIR that is uniquely their own. This version of 'DIR' will likely have little resemblance to the original. This will be the case, however well-intentioned, however devoted to the founding principles of DIR, these satellites may be. — Jarrod Jablonski^[2]

DIR criticisms and controversies[edit]

From its earliest days, some proponents of DIR have been critical of many other agencies, whose training they believe insufficient in fundamental diving skills.^[73] Although DIR system became well known in the field of long range, mixed gas, cave diving, it is claimed that its philosophy makes it both efficient and effective in different environments.^[74] This has been disputed by other individual divers and training agencies who claim that DIR is less optimal than other methods in particular situations.^[75] The British Cave Diving Group, for example, prefers to dive solo in caves, and argues that the DIR system, which relies on buddies and teams, presents problems for British caves that the CDG do not experience.^[76]

Solo diving[edit]

Some other training agencies also promote solo diving, and recommend practices that do not conform with DIR principles.

Controversies over DIR configurations suiting the developing skills, objectives and specific risks of recreational diving[edit]

Recreational diving is a very popular sport, with more than 25 million certifications issued by PADI alone.^[79] The reality is that in such a large and diverse diving population there is a very wide range of skills, abilities, and ambitions. Many divers dive infrequently - in a 1998 survey DEMA found that no more than a third of divers actually dived more than 10 times over a three-year period.^[80] With respect to this diverse diving population:

Acquisition of dive equipment is done in phases over an extended period of time and is subject to considerable budgetary constraint.^[88] A fully compliant DIR based system costs more than a simple recreational setup, meaning that moving through the phases of kit acquisition focused on DIR approval leads to having less personally owned equipment for much of the acquisition period. It has been argued that the lack of necessity to purchase a dive computer reduces DIR costs (Jablonski: 'Dive computers are expensive, and prevent divers with limited resources from purchasing truly useful equipment'^[89] '), it has also been argued that the lack of a dive computer adds to the risk of diving for recreational divers.^[90] Recreational dive equipment manufacturers provide equipment designed to provide a wide range of costs and performance characteristics in equipment, targeted at the range of uses and demands that recreational divers transition through as they acquire kit.

Controversy over DIR applicability to local practices in diving[edit]

Deep cave diving (as in the WKPP) has significant differences in hazards and environmental conditions from other types of recreational scuba diving. Conflicts occur where local diving practice experts say these conditions are so different that DIR system rationale and practices simply do not apply, and that DIR practices actually cause difficulties.^[91]

Criticism arising from DIR public relations and behavior[edit]

The rise of DIR from a local cave diving group of enthusiasts to a philosophy of diving followed by thousands, has been marked by persistent controversy. Part of this is due to sub-optimal public relations by some leaders and followers of the movement. Those who have had the most to say in public have often been least diplomatic in their criticism of both mainstream recreational and technical diving procedure, and the more obviously loose cannons of the opposing technical diving schools of thought.The core of the controversy surrounding DIR is in the phrase 'Doing It Right'. If a group is DIR, then all who are not doing things the DIR way are considered to be 'Doing it Wrong'.^[99] The use of the term 'stroke' to describe non-DIR divers has exacerbated tensions.^[100]

[P]ossibly the most important piece of wisdom in the diving world, and is something we should all apply to all of our diving. It is, simply, 'Don't dive with strokes.'

The term 'stroke' refers to someone who, knowing there is a better system, chooses to dive in a less than optimal way. It applies to those instructors who encourage students (who know no better) to exercise personal preference to sell more equipment. It applies to those who don't plan their dives, dive beyond their abilities, dive deep on air, take unnecessary risks, do big dives using unfamiliar gear, or whose only reason for diving is depth.

Diving with strokes moves us into an area where our safety is no longer in our own hands. Strokes are sometimes highly 'qualified'. Often they seem very confident - usually because they have no concept of the danger they are getting themselves, and you, into. — George M Irvine III^{[101][not in citation given]}

This generated a lot of argument, mostly on various internet forums. Many of these arguments devolved rapidly into braggadocio, name calling and foul language.^{[102][103][104]} The terms used in such accusatory arguments include:

• Strokery: the condition of being a non-DIR diver; statements supporting non-DIR points of view
• Strokeslamming: severe criticism of non-DIR divers or of their opinions

The vitriol expressed about other non-DIR diving practices and non-DIR diving personalities has been criticised as having gone well beyond the bounds of common decency and proper professional behaviour on many occasions. This criticism has especially been applied to statements made by George Irvine III. Several years after defining the DIR practices in his seminal 'Doing It Right' article, Irvine became involved in making a highly public and very offensive personal attack on Rob Palmer (founder of the International Technical Diving Association (ITDA) and one of the significant^{[105][106][107]} pioneers of technical and cave diving^[108]) at the time of Palmer's death in a diving accident. The remarks were so offensive that Irvine’s status as an instructor and a member of Technical Diving International were revoked.^[109] This was not an isolated incident. The strident nature of DIR claims to correctness are much inspired by George Irvine’s style, for example his attack on one of the most successful rebreather designs^[110] - the Buddy Inspiration. If anything, this strident approach has been totally counterproductive to the DIR movement.

There is no extant empiricism proving the DIR approach better than any other approach, and no formal engineering analysis (FMEA - as used for commercial diving) made to establish whether or not the DIR system provides improved safety and usability for all sport diving. Proponents of DIR point to the safety record and achievements of the WKPP,^[111][112]the 1999 GUE Britannic expedition,^[113]the Mexican Cave Exploration Project,^[114]and the recent exploration of the German aircraft carrier Graf Zeppelin by UTD divers^[115]as anecdotal evidence of the strength of the DIR system of diving, yet even under the stringent practices of the DIR system diving fatality still does occur.^[116]

Controversy about fundamental philosophy[edit]

There are strongly differing views between DIR authorities and other highly respected diving figures on the proper way a diver should go about choosing equipment in his/her diving configuration, and how safe the diver is in making these decisions.

Padi Advanced Open Water Manual Pdf

Padi Open Water Diver Manual Pdf

Comparisons between DIR and other recreational and technical diving groups[edit]

Because DIR's insistence on standardization is frequently misunderstood, it sometimes becomes a source of tension among divers. This is because some see the insistence on uniformity as an indictment of practices that do not abide by DIR principles. However, there is nothing essentially hostile or critical about DIR; in its most basic form, it is ultimately pragmatic, promoting the concept of uniformity within and among teams of divers. However, there is a certain degree of legitimate tension generated by imprudent advocates of DIR, who, having personally benefited from the system, become evangelical in promoting what they understand of its tenets. However, this is not an intrinsic weakness of DIR. All successful movements have their zealots. — Jarrod Jablonski^[2]

Trimix vs Deep air[edit]

The DIR approach requires the use of trimix below 100 feet (30 m). Most other agencies train divers to use compressed air or Nitrox to at least 130 feet (40 m);^[119] some use 'deep air' as deep as 180 feet (55 m)^[120] and at least one offers to train divers to use air as deep as 240 feet (73 m).^[121] In contrast DIR promotes the use of hyperoxic 30/30 trimix in the range of 100–120 feet.

Dive computers[edit]

The DIR philosophy is opposed to the use of dive computers. Most other technical diver training agencies recommend using two — a primary and a backup.Doing it Right: The Fundamentals of Better Diving page 119 lists 13 reasons why dive computers are bad. However, some of these appear strange - including the suggestion that they are expensive (modern dive computers are cheap, especially when compared with the cost of other equipment and diving gases recommended by the DIR approach), and too conservative (the approach to decompression promoted by DIR - ratio decompression - leads to decompression profiles of varying conservatism, but are often very conservative).^{[citation needed]}

Team diving[edit]

Most technical diving is focused on self-reliance,^[122] and creates an emphasis on solo diving mentality. DIR is solidly committed to buddy or 'team' diving.

Standardised equipment configuration[edit]

DIR requires that all divers in the team should have standardised equipment configurations to facilitate assistance. Whereas other conventional training agencies promote customising equipment for particular scenarios and individuals (sometimes called 'personal preference'), DIR strongly advocates everyone always being outfitted similarly (with the exception of task-specific equipment).Doing it Right: The Fundamentals of Better Diving page 67 says: 'It is the perfect system in zero visibility as well as in crystal clear water. The DIR system requires no modification to function effectively and efficiently in different environments ... In freezing water these divers use dry gloves and thicker undergarments and possibly electric heat. Cold water divers use slightly larger bolt-snaps. Otherwise, exactly the same system is used whether the dive is below ice or in the balmy tropics.'

Redundancy[edit]

While most training agencies preach the maximising of equipment redundancy,^{[citation needed]} in certain areas DIR opposes equipment redundancy; for example, the DIR approach is against dual bladder buoyancy compensators^[49]

Age[edit]

Most diver training agencies will train divers as young as 12,^[123] and some as young as 10 (or even 8 for pool diving).^[124] Agencies that promote DIR do not train divers younger than 16 (UTD),^[19] (GUE Rec 1),^[20] or 14 for divers certified by another agency (GUE Primer)^[21]

Associated organizations[edit]

• Global Underwater Explorers (GUE)
• Unified Team Diving (UTD)
• National Association of Underwater Instructors (NAUI)
• Woodville Karst Plain Project (WKPP)
• Inner Space Explorers (ISE)
• European Karst Plain Project (EKPP)
• Underwater Technical Research (UTRTek)

References[edit]

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7. ^ ^abGeorge Irvine in DIR3 video, downloaded from South Florida Dive Journal, http://sfdj.com/Videos.aspx
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11. ^Jablonski 2006, p. 20
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48. ^ ^{abcdefghijklmnopqrst}http://www.frogkick.nl/
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51. ^ ^abJablonski 2006, p. 92
52. ^Jablonski 2006, p. 91
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59. ^Jablonski 2006, pp. 103–104
60. ^ ^abcdStaff. 'DIR Equipment Configuration'. Global Underwater Explorers. Retrieved 8 February 2018.
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68. ^Halcyon website product description Diver Life Raft and Surf Shuttle http://www.halcyon.net/?q=node/11 accessed 23 December 2011
69. ^(in Dutch)Doing it right vs doing it wrong — frogkick.nl
70. ^http://www.frogkick.nl/ (in Dutch; click on 'non-DIR' at left)
71. ^http://www.frogkick.nl/ : click on 'Non-DIR' and then on 'suicide clips'
72. ^http://www.frogkick.nl : click on 'Non-DIR' and then on 'Gasswitch blok'
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74. ^Jablonski 2006, p. 67
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Bibliography[edit]

• Jablonski, Jarrod (2006). Doing it Right: The Fundamentals of Better Diving. Global Underwater Explorers. ISBN0-9713267-0-3.

External links[edit]

• DIRexplorers DIR Diving Internet Community
• PlongéeDIR Communauté francophone, entraînement, technique et exploration (En français)
• DiveDIR Includes an extensive step by step description of valve drill with a video clip and explanations of the reasoning behind each step
• DIR Diver Includes article on getting weighting correct