Deep diving has different meanings depending on the context. Even in recreational diving the meaning may vary:
- In recreational diving, a depth below about 30 metres (98 ft), where nitrogen narcosis becomes a significant hazard for most divers, may be considered a "deep dive"
- in recreational diving certification agencies, Deep diving, or Deep diver may be a certification awarded to divers that have been trained to dive to a specified depth range, generally deeper than 30 metres (98 ft).
- The Professional Association of Diving Instructors (PADI) defines anything from 18 metres (60 ft) to 30 metres (100 ft) as a "deep dive" (other diving organisations vary), and considers deep diving a form of technical diving. It is defined by the level of the diver's diver training, diving equipment, breathing gas, and surface support:
- In technical diving, a depth below about 60 metres (200 ft) where hypoxic breathing gas becomes necessary to avoid oxygen toxicity may be considered a "deep dive".
- In professional diving, a depth that requires special equipment, procedures, or advanced training is a deep dive.
Deep diving can mean something else in the commercial diving field. For instance early experiments carried out by Comex S.A. (Compagnie maritime d'expertises) using hydrox and trimix attained far greater depths than any recreational technical diving. One example being the Comex Janus IV open-sea dive to 501 metres (1,644 ft) in 1977. The open-sea diving depth record was achieved in 1988 by a team of Comex divers who performed pipe line connection exercises at a depth of 534 metres (1,752 ft) in the Mediterranean Sea as part of the Hydra 8 programme. These divers needed to breathe special gas mixtures because they were exposed to very high ambient pressure (more than 50 times atmospheric pressure).
An atmospheric diving suit allows very deep dives of up to 700 metres (2,300 ft). These suits are capable of withstanding the pressure at great depth permitting the diver to remain at normal atmospheric pressure. This eliminates the problems associated with breathing high pressure gases.
|12 metres (39 ft)||Recreational diving limit for divers aged under 12 years old and EN 14153-1 / ISO 24801-1 level 1 (Supervised Diver) standard.|
|18 metres (59 ft)||Recreational diving limit for divers with Open Water certification but without greater training and experience.|
|20 metres (66 ft)||Recreational diving limit for EN 14153-2 / ISO 24801-2 level 2 "Autonomous Diver" standard.|
|30 metres (98 ft)||Recommended recreational diving limit for divers. Average depth at which nitrogen narcosis symptoms begin to appear in adults.|
|40 metres (130 ft)||Absolute recreational diving limit for divers specified by Recreational Scuba Training Council (RSTC).
Maximum depth reachable by a French level 2 diver accompanied by an instructor (level 4 diver), breathing air.
|55 metres (180 ft)||Technical diving limit for "extended range" dives breathing air to a maximum ppO2 of 1.4 ATA.|
|60 metres (200 ft)||Maximum depth reachable by a French level 3 diver accompanied by another level 3 diver, breathing air.|
|66 metres (217 ft)||Depth at which compressed air results in an unacceptable risk of oxygen toxicity.[nb 2]|
|100 metres (330 ft)||Recommended technical diving limit. Maximum depth authorised for divers who have completed Trimix Diver certification with IANTD or Advanced Trimix Diver certification with TDI.|
|117 metres (384 ft)||Maurice Fargues was a volunteer in a programme to determine the maximum depth a scuba diver could reach with compressed air. He became the first diver to perish using scuba.|
|155 metres (509 ft)||Record depth for scuba dive on compressed air (not officially recognised).|
|200 metres (660 ft)||Limit for surface light penetration sufficient for plant growth, though minimal visibility possible farther down.[nb 3]|
|318 metres (1,043 ft)||World record for deepest dive on SCUBA.[nb 4]|
|534 metres (1,752 ft)||Comex Hydra 8 experimental dives. (1988)|
|610 metres (2,000 ft)||US Navy diver in Atmospheric Diving System (ADS) suit .|
Particular problems associated with deep dives
Deep diving has more hazards and greater risk than basic open water diving. Nitrogen narcosis, the “narks” or “rapture of the deep”, starts with feelings of euphoria and over-confidence but then leads to numbness and memory impairment similar to alcohol intoxication. Decompression sickness, or the “bends”, can happen if a diver ascends too fast, when excess inert gas leaves solution in the blood and tissues and forms bubbles. These bubbles produce mechanical and biochemical effects that lead to the condition. The onset of symptoms depends on the severity of the tissue gas loading and may develop during ascent in severe cases, but is frequently delayed until after reaching the surface. Bone degeneration (dysbaric osteonecrosis) is caused by the bubbles forming inside the bones; most commonly the upper arm and the thighs. Deep diving involves a much greater danger of all of these, and presents the additional risk of oxygen toxicity, which may lead to a convulsion underwater. Very deep diving using a helium–oxygen mixture (heliox) carries a risk of high pressure nervous syndrome. Coping with the physical and physiological stresses of deep diving requires good physical conditioning.
Using normal scuba equipment, breathing gas consumption is proportional to ambient pressure - so at 50 metres (160 ft), where the pressure is 6 bar, a diver breathes 6 times as much as on the surface (1 bar). Heavy physical exertion makes the diver breath even more gas, and gas becomes denser requiring increased effort to breathe with depth, leading to increasing risk of hypercapnia—an excess of carbon dioxide in the blood. The need to do decompression stops increases with depth. A diver at 6 metres (20 ft) may be able to dive for many hours without needing to do decompression stops. At depths greater than 40 metres (130 ft), a diver may have only a few minutes at the deepest part of the dive before decompression stops are needed. In the event of an emergency the diver cannot make an immediate ascent to the surface without risking decompression sickness. All of these considerations result in the amount of breathing gas required for deep diving being much greater than for shallow open water diving. The diver needs a disciplined approach to planning and conducting dives to minimise these additional risks.
Many of these problems are avoided by the use of surface supplied breathing gas, closed diving bells, and saturation diving, at the cost of logistical complexity, reduced maneuverability of the diver and greater expense.
Dealing with depth
Both equipment and procedures can be adapted to deal with the problems of greater depth. Usually the two are combined, as the procedures must be adapted to suit the equipment, and in some cases the equipment is needed to facilitate the procedures.
Equipment adaptations for deeper diving
The equipment used for deep diving depends on both the depth and the type of diving. Scuba is limited to equipment that can be carried by the diver, or is easily deployed by the dive team, while surface supplied diving equipment can be more extensive, and much of it stays above the water where it is operated by the support team.
- Scuba divers carry larger volumes of breathing gas to compensate for the increased gas consumption and decompression stops.
- Rebreathers manage gas much more efficiently than open circuit scuba, but are inherently more complex than open circuit scuba.
- Use of helium-based breathing gases such as trimix reduces nitrogen narcosis and stays below the limits of oxygen toxicity.
- A diving shot, a decompression trapeze or a decompression buoy can help divers return to their surface safety cover at the end of a dive.
- Decompression can be accelerated by using specially blended breathing gas mixtures.
- Surface supply of breathing gases reduces the risk of running out of gas.
- In-water decompression can be minimized by using dry bells and decompression chambers.
- Hot-water suits can prevent hypothermia due to the high heat loss when using helium based breathing gases.
- Diving bells and lockout submersibles expose the diver to the direct underwater environment for less time, and provide a relatively safe shelter that does not require decompression, with a dry environment where the diver can rest, take refreshment, and if necessary, receive first aid in an emergency.
- Breathing gas reclaim systems reduce the cost of using helium based breathing gases, by recovering and recycling exhaled surface supplied gas, analogous to rebreathers for scuba diving.
- The most radical equipment adaptation for deep diving is to isolate the diver from the direct pressure of the environment, using armoured atmospheric diving suits that allow diving to depths beyond those currently possible at ambient pressure. These rigid, articulated exoskeleton suits are sealed against water and withstand external pressure while providing life support to the diver for several hours at an internal pressure of approximately normal surface atmospheric pressure. This avoids the problems of inert gas narcosis, decompression sickness, barotrauma, oxygen toxicity, high work of breathing, compression arthralgia high pressure nervous syndrome and hypothermia, but at the cost of reduced mobility and dexterity, logistical problems due to the bulk and mass of the suits, and high equipment costs.
Procedural adaptations for deeper diving
Procedural adaptations for deep diving can be classified as those procedures for operating specialized equipment, and those that apply directly to the problems caused by exposure to high ambient pressures.
- The most important procedure for dealing with physiological problems of breathing at high ambient pressures associated with deep diving, is decompression. This is necessary to prevent inert gas bubble formation in the body tissues of the diver, which can cause severe injury. Decompression procedures have been derived for a large range of pressure exposures, using a large range of gas mixtures. These basically entail a slow and controlled reduction in pressure during ascent by using a restricted ascent rate and decompression stops, so that the inert gases dissolved in the tissues of the diver can be eliminated harmlessly during normal respiration.
- Saturation diving is a procedure used to reduce the high risk decompression a diver is exposed to during a long series of deep underwater exposures. By keeping the diver under high pressure for the whole job, and only decompressing at the end of several days to weeks of underwater work, a single decompression can be done at a slower rate without adding much overall time to the job. During the saturation period the diver lives in a pressurized environment at the surface, and is transported under pressure to the underwater work site in a closed diving bell.
|Nuno Gomes||Red Sea
|318 metres (1,043 ft)
270 metres (890 ft)
283 metres (928 ft)
252 metres (827 ft)
|Pascal Bernabé||Mediterranean||266 metres (873 ft)||2005|
|Krzysztof Starnawski||Red Sea||283 metres (928 ft)||2011|
|David Shaw[nb 5]||South Africa||271 metres (889 ft)||2004|
|Gilberto M de Oliveira||Brazil||274 metres (899 ft)||2002|
|John Bennett[nb 5]||Philippines
|310 metres (1,020 ft)
254 metres (833 ft)
|282 metres (925 ft)
251 metres (823 ft)
|Sheck Exley[nb 5]||South Africa
|263 metres (863 ft)
264 metres (866 ft)
|Don Shirley||South Africa||250 metres (820 ft)||2005|
|Hannes Keller||California||300 metres (980 ft)||1962|
|Mark Ellyatt||Andaman Sea
|313 metres (1,027 ft)
260 metres (850 ft)
|Dariusz Wilamowski||Lake Garda
|245 metres (804 ft)
264 metres (866 ft)
244 metres (801 ft)
Amongst technical divers, there are divers who participate in ultra-deep diving on SCUBA below 200 metres (660 ft). This practice requires high levels of training, experience, discipline, fitness and surface support. Only twelve persons are known to have ever dived below a depth of 240 metres (790 ft) on self-contained breathing apparatus recreationally.[nb 6][nb 7] That is fewer than the number of people who have flown to the moon. The Holy Grail of deep scuba diving was the 300 m (980 ft) mark, first achieved by John Bennett in 2001, and has only been achieved five times since.
Ultra deep air
While extreme deep diving on air is extremely dangerous, before the popularity of Trimix attempts were made to set world record depths using conventional air. This created an extreme risk of both narcosis and oxygen toxicity in the divers and contributed to a high fatality rate amongst those attempting records. In his book, Deep Diving, Bret Gilliam chronicles the various fatal attempts to set records as well as the smaller number of successes. From the comparatively few who survived extremely deep air dives:
- 1947 Frédéric Dumas, a colleague of Jacques Cousteau, dived to 94 metres (308 ft) on air
- 1947 Maurice Fargues, another colleague of Jacques Cousteau, dived to 117 metres (384 ft) on air but died after losing consciousness at depth
- 1959 Ennio Falco reported having reached a depth of 133 metres (436 ft) on air, but had no means to record it
- 1965 Tom Mount and Frank Martz dive to a depth of 110 metres (360 ft) on air
- 1967 Hal Watts and AJ Muns dive to a depth of 120 metres (390 ft) on air
- 1968 Neil Watson and John Gruener dived to 133 metres (436 ft) on air in the Bahamas. Watson reported that he had no recollection at all of what transpired at the bottom of the descent due to narcosis.
- 1971 Sheck Exley dived to 142 metres (466 ft) on air on December 11 near Andros Island in the Bahamas. Exley was only supposed to go down to 91 metres (299 ft) in his capacity as a safety diver (although he'd practiced several dives to 120 metres (390 ft) in preparation), but descended to search for the dive team after they failed to return on schedule. Exley almost made it to the divers, but was forced to turn back due to heavy narcosis and nearly blacking out.
- 1990 Bret Gilliam dived to a depth of 138 metres (453 ft) on air. Unusually, Gilliam remained largely functional at depth and was able to complete basic maths problems and answer simple questions written on a slate by his crew beforehand.
- 1993 Bret Gilliam extended his own world record to 145 metres (476 ft), again reporting no ill effects from narcosis or oxygen toxicity.
- 1994 Dan Manion set the current record for a deep dive on air at 155 metres (509 ft). Manion reported he was almost completely incapacitated by narcosis and has no recollection of time at depth.
In deference to the high death rate, the Guinness World Records ceased to publish records on deep air dives in mid-2005.
- Decompression sickness
- Breathing gas
- Free-diving, diving without breathing
- High pressure nervous syndrome
- Oxygen toxicity
- Brylske, A. (2006). Encyclopedia of Recreational Diving, 3rd edition. United States: PADI. ISBN 1-878663-01-1.
- 1965-2000 — 36 years of deep diving and submarine techniques development, from COMEX Hyperbaric Experimental Centre at the Wayback Machine (archived October 13, 2007)
- Hydra 8: Pre-commercial Hydrogen Diving Project
- Extreme Environment Engineering Departement Hyperbaric Experimental Centre - History at the Wayback Machine (archived October 5, 2008)
- Staff. "Competencies of a recreational scuba diver at level 1 "Supervised Diver"". EUF Certification International. Retrieved 29 September 2013.
- Staff. "Competencies of a recreational scuba diver at level 2 "Autonomous Diver"". EUF Certification International. Retrieved 29 September 2013.
- Matsen, Brad (2009). Jacques Cousteau: The Sea King. New York: Pantheon Books. pp. 73, 76–79, 85. ISBN 978-0-375-42413-7.
- Set by Dr Dan Marion on March 18, 1994. The record is not officially recognised anywhere, and it should be noted that Dr Marion's second dive computer only registered a depth of 490 feet. See generally Deep Diving by Bret Gilliam, ISBN 0-922769-31-1, at pages 35 and following.
- Navy diver sets world record
- Egstrom GH (2006). "Historic Perspective: Scientific Deep Diving and the Management of the Risk". In: Lang, MA and Smith, NE (eds). Proceedings of Advanced Scientific Diving Workshop (Smithsonian Institution, Washington, DC). Retrieved 2008-07-05.
- Southerland, DG (2006). "Medical Fitness at 300 FSW". In: Lang, MA and Smith, NE (eds). Proceedings of Advanced Scientific Diving Workshop (Smithsonian Institution, Washington, DC). Retrieved 2008-07-05.
- Gomes, N. "Verified dives below 200 metres". Retrieved 2008-06-14.
- Scubarecords.com. "Recorded Deep Dives Below 200 m". Retrieved 2008-06-14.
- Deep Diving, an advanced guide to physiology, procedures and systems. Bret Gilliam. 1995-01-25. ISBN 978-0-922769-31-5. Retrieved 2009-11-19.
- Exley, Sheck. Caverns Measureless to Man
- All depths specified for sea water. Fractionally deeper depths may apply in relation to freshwater due to its lower density
- Oxygen toxicity depends upon a combination of partial pressure and time of exposure, individual physiology, and other factors not fully understood. NOAA recommends that divers do not expose themselves to breathing oxygen at greater than 1.6 bar ppO2, which occurs at 66 metres (217 ft) breathing air.
- Assuming crystal clear water; surface light may disappear completely at much shallower depths in murky conditions. Minimal visibility is still possible far deeper. Deep sea explorer William Beebe reported seeing blueness, not blackness, at 1400 feet (424 metres). "I peered down and again I felt the old longing to go farther, although it looked like the black pit-mouth of hell itself---yet still showed blue." (William Beebe, "A Round Trip to Davey Jones's Locker," The National Geographic Magazine, June 1931, p. 660.)
- Guinness World Records recognises the 1,044 feet dive by Nuno Gomes as the current official world record.
- Subsequently died during diving accidents.
- Statistics exclude military divers (classified), and commercial divers (commercial diving to those depth is on scuba is not permitted by occupational health and safety legislation). In 1989, the US Navy experimental diving unit published a paper entitled EX19 [a type of experimental rebreather] Performance Testing at 850 and 450 FSW that included a section on results from tests on the use of rebreathers at 850 feet.Knafelc, ME (1989). "EX 19 Performance Testing at 850 and 450 FSW (Feet of Seawater)". US Naval Experimental Diving Unit Technical Report. NEDU-8-89. Retrieved 2008-07-24.
- In 2007 a Turkish Navy diver dived to a depth of 998 feet (304 m) off the coast of Cyprus, but that dive has not been independently verified. He used a closed-circuit rebreather. His dive was aborted due to equipment failure. It was a Turkish Navy experimental dive.
- Dent, W (2006). "AAUS Deep Diving Standards". In: Lang, MA and Smith, NE (eds). Proceedings of Advanced Scientific Diving Workshop (Smithsonian Institution, Washington, DC). Retrieved 2008-07-05.