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Trimix is a breathing gas consisting of oxygen, helium and nitrogen and is used in deep commercial diving, during the deep phase of dives carried out using technical diving techniques, and in advanced recreational diving.
Technical diving is scuba diving that exceeds the agency-specified limits of recreational diving for non-professional purposes. Technical diving may expose the diver to hazards beyond those normally associated with recreational diving, and to a greater risk of serious injury or death. Risk may be reduced via appropriate skills, knowledge, and experience. Risk can also be managed by using suitable equipment and procedures. The skills may be developed through specialized training and experience. The equipment involves breathing gases other than air or standard nitrox mixtures, and multiple gas sources.
Deep diving is underwater diving to a depth beyond the norm accepted by the associated community. In some cases this is a prescribed limit established by an authority, while in others it is associated with a level of certification or training, and it may vary depending on whether the diving is recreational, technical or commercial. Nitrogen narcosis becomes a hazard below 30 metres (98 ft) and hypoxic breathing gas is required below 60 metres (200 ft) to lessen the risk of oxygen toxicity.
Altitude diving is underwater diving using scuba or surface supplied diving equipment where the surface is 300 metres (980 ft) or more above sea level. Altitude is significant in diving because it affects the decompression requirement for a dive, so that the stop depths and decompression times used for dives at altitude are different from those used for the same dive profile at sea level. The U.S. Navy tables recommend that no alteration be made for dives at altitudes lower than 91 metres (299 ft) and for dives between 91 and 300 meters correction is required for dives deeper than 44 metres (144 ft) of sea water. Most recently manufactured decompression computers can automatically compensate for altitude.
Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other cave users. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave-diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave-diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave-diving and cavern-diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified.
Sheck Exley was an American cave diver. He is widely regarded as one of the pioneers of cave diving, and he wrote two major books on the subject: Basic Cave Diving: A Blueprint for Survival and Caverns Measureless to Man. On February 6, 1974, Exley became the first chairman of the Cave Diving Section of the American National Speleological Society. During his career, he established many of the basic safety procedures used in cave and overhead diving today. Exley was also a pioneer of extreme deep scuba diving.
Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.
Boesmansgat, also known in English as "Bushman's Hole", is a deep submerged freshwater cave in the Northern Cape province of South Africa, which has been dived to a depth of 282.6 metres (927 ft).
A diving watch, also commonly referred to as a diver's or dive watch, is a watch designed for underwater diving that features, as a minimum, a water resistance greater than 1.1 MPa (11 atm), the equivalent of 100 m (330 ft). The typical diver's watch will have a water resistance of around 200 to 300 m, though modern technology allows the creation of diving watches that can go much deeper. A true contemporary diver's watch is in accordance with the ISO 6425 standard, which defines test standards and features for watches suitable for diving with underwater breathing apparatus in depths of 100 m (330 ft) or more. Watches conforming to ISO 6425 are marked with the word DIVER'S to distinguish ISO 6425 conformant diving watches from watches that might not be suitable for actual scuba diving.
A dive profile is a description of a diver's pressure exposure over time. It may be as simple as just a depth and time pair, as in: "sixty for twenty," or as complex as a second by second graphical representation of depth and time recorded by a personal dive computer. Several common types of dive profile are specifically named, and these may be characteristic of the purpose of the dive. For example, a working dive at a limited location will often follow a constant depth (square) profile, and a recreational dive is likely to follow a multilevel profile, as the divers start deep and work their way up a reef to get the most out of the available breathing gas. The names are usually descriptive of the graphic appearance.
John Bennett was a British scuba diver who set a world record by becoming the first person to deep dive below a depth of 300 m (1,000 ft) on self-contained breathing apparatus on 6 November 2001. Bennett first broke the record in 1999 when he reached 200 m (660 ft) accompanied by Chuck Driver. In 2000 Bennett set a new record of 254 m (833 ft), before his final record-breaking dive to 308 m (1,010 ft) in 2001. Having founded Atlantis Dive in the Philippines in the late 1990s, Bennett and his world record breaking team, including Ron Loos, Mark Cox and Targa Mann went on to establish Tech Dive Academy in Port Douglas, Australia. In the early 2000s, Bennett and Loos made the first dives to the MV Princess of the Orient wreck site, which is located off Fortune Island, outside and to the south of Manila Bay. In 2001, he located the wreck of the Imperial Japanese Navy dreadnought Yamashiro in the Surigao Strait through sound scans, but could not confirm it before his death. Confirmation was not made until 2017.
David John Shaw was an Australian scuba diver, technical diver, and airline pilot for Cathay Pacific, flying the Lockheed L-1011 Tristar, then the 747-400, and then the A330-300, A340-300, and A340-600. He flew for Cathay Pacific from 1989 until his death in 2005. Before flying for Cathay Pacific, he flew for Mission Aviation Fellowship in Papua New Guinea and Tanzania. He also flew agricultural aircraft in South Australia and New South Wales.
Pascal Bernabé is a French scuba diver who in 2005 laid claim to the world best for depth on a deep dive using self-contained breathing apparatus. Bernabé claimed to have reached a maximum depth of 330 metres (1,080 ft) using trimix on 5 June 2005 near Propriano, Corsica. This was actually deeper than the official deepest scuba dive recognized by Guinness World Records at the time. That mark, set by Nuno Gomes in Dahab, Egypt, was 318.25 metres (1,044.1 ft) of sea water. However, Bernabé's claimed deepest dive was not included in the Guinness Book of World Records due to insufficient evidence of such a dive ever being performed.
Deon Dreyer was a South African recreational scuba diver who died in Bushman's Hole in South Africa. Cave diver David Shaw died more than 10 years later while attempting to retrieve Dreyer's body.
In underwater diving, ascending and descending is done using strict protocols to avoid problems caused by the changes in ambient pressure and the hazards of obstacles near the surface such as collision with vessels. Diver certification and accreditation organisations place importance on these protocols early in their diver training programmes. Ascent and descent are historically the times when divers are injured most often when failing to follow appropriate procedure.
To prevent or minimize decompression sickness, divers must properly plan and monitor decompression. Divers follow a decompression model to safely allow the release of excess inert gases dissolved in their body tissues, which accommodated as a result of breathing at ambient pressures greater than surface atmospheric pressure. Decompression models take into account variables such as depth and time of dive, breathing gasses, altitude, and equipment to develop appropriate procedures for safe ascent.
The following outline is provided as an overview of and topical guide to underwater diving:
The following index is provided as an overview of and topical guide to underwater diving:
Cave diving is underwater diving in water-filled caves. The equipment used varies depending on the circumstances, and ranges from breath hold to surface supplied, but almost all cave diving is done using scuba equipment, often in specialised configurations with redundancies such as sidemount or backmounted twinset. Recreational cave diving is generally considered to be a type of technical diving due to the lack of a free surface during large parts of the dive, and often involves planned decompression stops. A distinction is made by recreational diver training agencies between cave diving and cavern diving, where cavern diving is deemed to be diving in those parts of a cave where the exit to open water can be seen by natural light. An arbitrary distance limit to the open water surface may also be specified. Despite the risks, water-filled caves attract scuba divers, cavers, and speleologists due to their often unexplored nature, and present divers with a technical diving challenge.
References
- ↑ Venter, Pieter. "Short biography of Nuno Gomes". NunoGomes.co.za. Archived from the original on 7 August 2017. Retrieved 6 April 2015.
- ↑ "Nuno Gomes". Sterling divers. Archived from the original on 6 December 2018. Retrieved 18 June 2023.
- ↑ "South African Nuno Gomes now world's deepest scuba diver". CDNN.info. Archived from the original on 15 June 2005.
- ↑ "World Record Cave Dive". Karst Worlds. Retrieved 29 August 2021.
