Deep Dive Into History

[Stephani Kapnick]

Deepdiving 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.

For some recreational diving 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). However, the Professional Association of Diving Instructors (PADI) defines anything from 18 to 30 metres (59 to 98 ft) as a "deep dive" in the context of recreational diving (other diving organisations vary), and considers deep diving a form of technical diving.[1][page needed] 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 may be considered a deep dive.

Deep diving can mean something else in the commercial diving field. For instance early experiments carried out by COMEX using heliox and trimix attained far greater depths than any recreational technical diving. One example being its "Janus 4" open-sea dive to 501 metres (1,640 ft) in 1977.[2][3]

The open-sea diving depth record was achieved in 1988 by a team of COMEX and French Navy divers who performed pipeline connection exercises at a depth of 534 metres (1,750 ft) in the Mediterranean Sea as part of the "Hydra 8" programme employing heliox and hydrox. The latter avoids the high-pressure nervous syndrome (HPNS) caused by helium and eases breathing due to its lower density.[2][4][5] These divers needed to breathe special gas mixtures because they were exposed to very high ambient pressure (more than 54 times atmospheric pressure).

An atmospheric diving suit (ADS) allows very deep dives of up to 700 metres (2,300 ft).[6] 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 pressurised gases. In 2006 Chief Navy Diver Daniel Jackson set a record of 610 metres (2,000 ft) in an ADS.[7][8]

On 20 November 1992 COMEX's "Hydra 10" experiment simulated a dive in an onshore hyperbaric chamber with hydreliox. Tho Mavrostomos spent two hours at a simulated depth of 701 metres (2,300 ft).[2][9][10][11][12]

Deep diving has more hazards and greater risk than basic open-water diving.[26] 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.[1][page needed] Decompression sickness, or the "bends", can happen if a diver ascends too rapidly, 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.[1][page needed] 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 convulsions underwater. Very deep diving using a helium-oxygen mixture (heliox) or a hydrogen-helium-oxygen mixture (hydreliox) carries the risk of high-pressure nervous syndrome and hydrogen narcosis. Coping with the physical and physiological stresses of deep diving requires good physical conditioning.[27]

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.

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.

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 diving support team.[citation needed]

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.

Amongst technical divers, there are divers who participate in ultra-deep diving on scuba below 200 metres (656 ft). This practice requires high levels of training, experience, discipline, fitness and surface support. Only twenty-six people are known to have ever dived to at least 240 metres (790 ft) on self-contained breathing apparatus recreationally.[20][28][nb 4][nb 5] The "Holy Grail" of deep scuba diving was the 300 metres (980 ft) mark, first achieved by John Bennett in 2001, and has only been achieved five times since.[citation needed]

The difficulties involved in ultra-deep diving are numerous. Although commercial and military divers often operate at those depths, or even deeper, they are surface supplied. All of the complexities of ultra-deep diving are magnified by the requirement of the diver to carry (or provide for) their own gas underwater. These lead to rapid descents and "bounce dives". This has led to extremely high mortality rates amongst those who practice ultra-deep diving.[citation needed] Notable ultra-deep diving fatalities include Sheck Exley, John Bennett, Dave Shaw and Guy Garman. Mark Ellyatt, Don Shirley and Pascal Bernab were involved in serious incidents and were fortunate to survive their dives. Despite the extremely high mortality rate, the Guinness World Records continues to maintain a record for scuba diving[25] (although the record for deep diving with compressed air has not been updated since 1999, given the high accident rate). Amongst those who do survive significant health issues are reported. Mark Ellyatt is reported to have suffered permanent lung damage; Pascal Bernab (who was injured on his dive when a light on his mask imploded[29]) and Nuno Gomes reported short to medium term hearing loss.[30][unreliable source?]

In addition, "ordinary" risks like size of gas reserves, hypothermia, dehydration and oxygen toxicity are compounded by extreme depth and exposure.and long in-water decompression times Some technical diving equipment is simply not designed for the greater pressuresses at these depths, and reports of key equipment (including submersible pressure gauges) imploding are not uncommon.[citation needed]

A severe risk in ultra-deep air diving is deep water blackout, or depth blackout, a loss of consciousness at depths below 50 metres (160 ft) with no clear primary cause, associated with nitrogen narcosis, a neurological impairment with anaesthetic effects caused by high partial pressure of nitrogen dissolved in nerve tissue, and possibly acute oxygen toxicity.[71] The term is not in widespread use at present, as where the actual cause of blackout is known, a more specific term is preferred. The depth at which deep water blackout occurs is extremely variable and unpredictable.[72] Before the popular availability of trimix, attempts were made to set world record depths using air. The extreme risk of both narcosis and oxygen toxicity in the divers contributed to a high fatality rate in 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.[73] From the comparatively few who survived extremely deep air dives:

Until now, only two people have successfully made it to the bottom of Challenger Deep, the planet's deepest point at the southern end of the Mariana Trench. Back in 1960, oceanographer Don Walsh was the first to make it down to the trench successfully, reaching about 35,814 feet (10,916 m). He took the journey with Swiss oceanographer and engineer Jacques Piccard. [In Photos: James Cameron's Epic Dive to Challenger Deep]

It was chilly; it was quiet; and "it was so very peaceful," he told Live Science. "I was surrounded by enormous pressure, but I was safely cocooned in my technological bubble." The pressure at that depth is about 16,000 pounds per square inch, over a thousand times more than the pressure at sea level. After Vescovo's record-breaking dive, other team members took four other subsequent dives to the trench.

In the depths, during those five dives, they discovered red and yellow rocky outcrops that could be chemical deposits or bacterial mats, which are made by chemosynthetic microbes, meaning they can convert carbon-containing molecules into organic matter.

At the deepest point, they were accompanied by some transparent bottom-dwelling sea cucumbers (Holothurians) and an amphipod called the Hirondellia gigas. Because on previous missions these amphipods have been found to have microplastics in their guts, the team collected samples to test how much. Sitting there in the deepest point of the planet, Vescovo also came across a plastic bag and candy wrappers.

"Honestly, toward the end, I simply turned the thrusters off, leaned back in the cockpit and enjoyed a tuna fish sandwich while I very slowly drifted just above the bottom of the deepest place on Earth, enjoying the view and appreciating what the team had done technically," Vescovo said. "It was a very happy, peaceful moment for me."

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