An aquanaut is any person who remains underwater, breathing at the ambient pressure for long enough for the concentration of the inert components of the breathing gas dissolved in the body tissues to reach equilibrium, in a state known as saturation. Usually this is done in an underwater habitat on the seafloor for a period equal to or greater than 24 continuous hours without returning to the surface. The term is often restricted to scientists and academics, though there were a group of military aquanauts during the SEALAB program. Commercial Divers in similar circumstances are referred to as Saturation Divers. An aquanaut is distinct from a submariner, in that a submariner is confined to a moving underwater vehicle such as a submarine that holds the water pressure out. Aquanaut derives from the Latin word aqua ("water") plus the Greek nautes ("sailor"), by analogy to the similar construction "astronaut".
The first human aquanaut was Robert Sténuit, who lived on board a tiny one-man cylinder at 200 feet (61 m) for 24 hours in September 1962 off Villefranche-sur-Mer on the French Riviera. Military aquanauts include Robert Sheats, author Robin Cook, and astronauts Scott Carpenter and Alan Shepard. Civilian aquanaut Berry L. Cannon died of carbon dioxide poisoning during the U.S. Navy's SEALAB III project. Scientific aquanauts include Richard Cooper, Stephen Neudecker, Al Waterfield, Jonathan Helfgott, Robert Dill, Sylvia Earle, Ian Koblick, Neil Monney, Chris Olstad, Joseph B. MacInnis, John Perry, Harold "Wes" Pratt (on whom the character Matt "Winch" Hooper in Jaws was based), Phillip Sharkey, Dick Rutkowski, Alina Szmant, Bill High, Phil Nuytten, Matthew Morgan, Steven Miller, Morgan Wells, C. Lavett Smith and about 700 others, including the crew members (many of them astronauts) of NASA's NEEMO missions at the Aquarius underwater laboratory.
A Nigerian ship's cook, Harrison Odjegba Okene, survived for 60 hours in a sunken tugboat, Jascon-4, that capsized on 26 May 2013 in heavy seas while it was stabilising an oil tanker at a Chevron platform in the Atlantic Ocean about 32km (20 miles) off the Nigerian coast. Eleven crew members died, but Okene survived for almost three days by finding an air pocket which kept him alive until he was discovered by South African divers employed by the DCN global diving company to investigate and recover bodies. He was transferred to a closed diving bell and returned to the surface for decompression from saturation. The ship was on the bottom at a depth of 30 metres (98 ft). Okene found his way into the engineer's office where an airspace of about 1.2m height was sufficient to keep him alive, He managed to contrive a platform from a mattress which kept the upper part of his body above water and helped reduce heat loss.
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