Deep diving

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The meaning of the term deep diving is a form of technical diving.^[1] It is defined by the level of the diver's diver training, diving equipment, breathing gas, and surface support:

• in recreational diving, 30 metres / 100 feet may be a "deep dive"
• in technical diving, 60 metres / 200 feet may be a "deep dive"
• in surface supplied diving, 100 metres / 330 feet may be a "deep dive"

Deep Diving

Depth[nb 1]	Comments
40 feet/12 meters	Recreational diving limit for divers aged under 12 years old and beginner divers.
60 feet/18 meters	Recreational diving limit for divers with Open Water certification but without greater training and experience.
100 feet/30 meters	Recommended recreational diving limit for divers.[1] Average depth at which nitrogen narcosis symptoms begin to appear in adults.
130 feet/40 meters	Absolute recreational diving limit for divers specified by Recreational Scuba Training Council (RSTC).[1]
180 feet/55 meters	Technical diving limit for "extended range" dives breathing air to a maximum ppO2 of 1.4 ATA.
218 feet/65 meters	Depth at which compressed air results in an unacceptable risk of oxygen toxicity[nb 2]
330 feet/100 meters	Technical diving training limit for divers breathing trimix. Recommended technical diving limit.
660 feet/200 meters	Absolute limit for surface light penetration[nb 3]
1,083 feet/330 meters	World record for deepest dive on SCUBA[nb 4]

Contents 1 Particular problems associated with deep dives 2 Dealing with depth 3 Ultra-deep diving 4 See also 5 References 6 Footnotes 7 Further reading 8 External links

[edit] Particular problems associated with deep dives

Deep diving obviously has more consequences and dangers than basic open water diving.^[2] Nitrogen narcosis, or the “narks” or “rapture of the deep”, starts with feelings of euphoria and over-confidence but then lead to numbness and memory impairment similar to alcohol intoxication. Decompression sickness, or the “bends”, is when the gas bubbles of nitrogen get caught in the joints on an ascent. Yet, the effects tend to be delayed until reaching the surface. Bone degeneration (dysbaric osteonecrosis) is caused by the bubbles forming inside the bones; most commonly the upper arm and the thighs. Air embolism causes loss of consciousness and speech and visual problems. This tends to be life threatening, but sometimes the symptoms resolve before the recompression chamber are needed. All these are harms and possibly worse effects of deep diving. These physical and physiological stresses require good physical conditioning.^[3]

• High breathing gas consumption. Gas consumption is proportional to pressure - so at 50 metres / 165 feet (6 bar) a diver breathes 6 times as much as on the surface (1 bar). Heavy physical exertion causes even more gas to be breathed.
• Increased nitrogen narcosis. This causes stress and inefficient thinking in the diver. When breathing air many divers find 40 metres / 130 feet a safe maximum depth.
• The need to do decompression stops increases with depth. A diver at 6 metres may be able to dive for many hours without needing to do decompression stops. At depths greater than 40 metres / 130 feet, 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. The diver needs a disciplined approach to planning and conducting dives and needs to carry extra gas for the decompression stops to reduce the risk of being unable to complete the stops.
• Drifting. If long decompression stops are carried out in a tidal current, the divers may drift away from their boat cover or a safe exit point on the shore.
• Increased breathing effort. Gas becomes denser and the effort required to breathe increases with depth (work of breathing).
• Increasing risk of hypercapnia, an excess of carbon dioxide in the blood.
• Oxygen toxicity.
• High pressure nervous syndrome.

[edit] Dealing with depth

• Carry larger volumes of breathing gas to compensate for the increased gas consumption and decompression stops.
• Rebreathers are much more efficient consumers of gas than open circuit scuba and inherently more complex than open circuit scuba.
• Use helium-based breathing gases such as trimix to reduce nitrogen narcosis and stay beyond 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.

[edit] Ultra-deep diving

Amongst technical divers, there are certain elite divers who participate in ultra-deep diving on SCUBA (using closed circuit rebreathers and heliox) below 660 feet/200 metres. Ultra-deep diving requires extraordinarily high levels of training, experience, fitness and surface support. Only eight (or possibly nine) persons are known to have ever dived below a depth of 800 feet (240 m) on self contained breathing apparatus recreationally.^{[4][5][nb 5]} That is fewer than the number of people who have walked on the surface of the moon. The Holy Grail of deep diving was the 1,000 ft (300 m) mark, first achieved by John Bennett in 2001, and has only been achieved twice since.

Verified dives below 800 feet

Name	Location	Depth	Year
Nuno Gomes	Red Sea Red Sea South Africa South Africa	1,044 feet 890 feet 927 feet 826 feet	2005 2004 1996 1994
Pascal Bernabé	Mediterranean Mediterranean	1,083 feet 873 feet	2005 2005
David Shaw[nb 6]	South Africa	888 feet	2004
G.M de Oliveira	Brazil	898 feet	2002
John Bennett[nb 6]	Philippines Philippines	1,010 feet 833 feet	2001 2001
Jim Bowden	Mexico Mexico	925 feet 825 feet	1994 1993
Sheck Exley[nb 6]	South Africa Mexico	863 feet 867 feet	1993 1989
Don Shirley	South Africa	820 feet	2005

In 2003 Mark Ellyatt is believed to have dived to a depth of 1,032 feet (315 m), but that dive has not been independently verified.

All of the foregoing dives were conducted on open circuit SCUBA equipment, except for David Shaw, who used a closed-circuit rebreather.

In 2007 Erdogan Bayburt, a former 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.^{[citation needed]}

[edit] See also

• Decompression sickness
• Breathing gas
• Heliox
• Hydreliox
• High pressure nervous syndrome
• Oxygen toxicity
• Trimix

[edit] References

[edit] Footnotes

1. ^ All depths specified for sea water. Fractionally deeper depths may apply in relation to freshwater due to its lower density
2. ^ 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 218 feet breathing air.
3. ^ Assuming crystal clear water; surface light may disappear completely at much shallower depths in murky conditions.
4. ^ 1,083 feet was the depth reportedly achieved by Pascal Bernabé in 2005. However, the Guinness World Records still recognises the 1,044 feet dive by Nuno Gomes (diver) earlier in the same year as the current official world record.
5. ^ Statistics exclude military divers (classified), and commercial divers (although commercial diving to that depth is unknown on SCUBA). 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 which 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. http://archive.rubicon-foundation.org/7423. Retrieved on 2008-07-24. 
6. ^ ^{a b c d} Subsequently died during diving accidents.

[edit] Further reading

• Dent, W (2006). "AAUS Deep Diving Standards.". In: Lang, MA and Smith, NE (eds). Proceedings of Advanced Scientific Diving Workshop (Washington, DC). http://archive.rubicon-foundation.org/4669. Retrieved on 2008-07-05. 

[edit] External links

• Recreational Deep Diving

v • d • e Underwater diving Types: Scuba diving · Surface supplied diving · Free-diving · Snorkelling · Saturation diving Specialities: Technical diving · Deep diving · Decompression diving · Mixed gas diving · Wreck diving · Cave diving · Ice diving · Rebreather diving · Solo diving · Altitude diving Equipment: Diving suit · Scuba set · Rebreather · Dive computer · Diver propulsion vehicle · Mask · Fins · Snorkel · Buoyancy control device Disciplines: Professional diving · Police diving · Military diving · Underwater photography · Underwater videography Hazards: Decompression sickness · Nitrogen narcosis · Oxygen toxicity · Barotrauma · Hyperbaric medicine · Drowning · Shallow water blackout · Deep water blackout · High pressure nervous syndrome · Dysbaric osteonecrosis

v • d • e Diving decompression Diving Scuba diving · Recreational diving · Deep diving  · Technical diving · Saturation diving Equipment Decompression trapeze · Decompression tables · Recreational Dive Planner · Dive computer · Diving chamber · Jonline · Decompression buoy Gases Trimix · Nitrox · Oxygen · Air · Gas blending Injury Decompression sickness  · Hyperbaric medicine  · Decompression chamber  · Recompression chamber Miscellaneous Decompression stop · Decompression schedule · Decompression curve · No Decompression Limit · In-water recompression · Deco on the fly  · Ratio decompression Algorithms Bühlmann decompression algorithm · Reduced Gradient Bubble Model · Thalmann Algorithm · Varying Permeability Model