Sheck Exley (April 1, 1949 – April 6, 1994) was an

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

cave diver 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 ...

. 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 The National Speleological Society (NSS) is an organization formed in 1941 to advance the exploration, conservation, study, and understanding of caves in the United States. Originally headquartered in Washington D.C., its current offices are in ...

. 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. For purposes of rescue during cave diving, Exley helped standardize the usage of the "octopus", a redundant second stage

diving regulator A diving regulator is a pressure regulator that controls the pressure of breathing gas for diving. The most commonly recognised application is to reduce pressurized breathing gas to ambient pressure and deliver it to the diver, but there are als ...

that can be used as a backup in the event the diver's primary second stage fails, or alternatively, to allow the diver and his buddy to have simultaneous access to the diver's gas if the buddy has an out-of-gas emergency. The octopus is now considered an essential piece of equipment among virtually all scuba divers, whether caving or in open water. He died at age 45 while trying to set a depth record by diving the world's deepest sinkhole, Mexico's deep, Zacatón, a fresh water

cenote A cenote ( or ; ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater. The regional term is specifically associated with the Yucatán Peninsula of Mexico, where cenotes were commonly used ...

. In the book, ''Diving into Darkness'' (a story about

Dave Shaw David John Shaw (20 July 1954 – 8 January 2005) was an Australian Scuba diving, scuba diver, technical diving, technical diver, and airline pilot for Cathay Pacific, flying the Lockheed L-1011 TriStar, Lockheed L-1011 Tristar, then the B ...

and Don Shirley), the author comments: "Exley's status in the sport is almost impossible to overstate".

Early life and career outside of diving

Exley began diving in 1965 at the age of 16. That same year he entered his first cave and was hooked on cave diving for the rest of his life. To finance this passion, Exley worked as a mathematics teacher at Suwannee High School in Live Oak, Florida. In spring 1973, Exley served as an

aquanaut 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 satura ...

during an eight-day mission aboard the Hydrolab underwater habitat in

the Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the a ...

Records

Exley was the first in the world to log over 100 cave dives (at the age of 23); in 29 years of cave diving he made over 4000 dives. Exley had an unusual resistance to nitrogen narcosis, and was one of the few divers to survive a open-water dive on simple compressed air. In acting as a safety diver for two divers trying to set an air-only depth record in 1970, Exley reached in salt water, but could go no deeper due to narcosis and the start of blackout (the two record-depth attempting unconscious divers died just out of reach beneath him, Interview with Exley. and such air-depth records are no longer sought or recorded). During his diving career, he set numerous depth and cave penetration records. Exley was the first person in the history of technical SCUBA diving to dive below , a feat only 20 people have performed . His carefully planned multistage decompressions from these dives, in open water (not in a decompression tank), sometimes required times of as much as 13.5 hours. However, he never suffered a classic case of

decompression sickness Decompression sickness (abbreviated DCS; also called divers' disease, the bends, aerobullosis, and caisson disease) is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompressio ...

in his career. Exley and German cave diver

Jochen Hasenmayer Jochen Hasenmayer (born 28 October 1941 in Pforzheim, Germany) is a German speleologist and cave diver from Birkenfeld in Baden-Württemberg, whose spectacular dives have frequently made headlines. Cave diving Hasenmayer began his cave divin ...

became friends and rivals in the 1980s, each repeatedly attempting to break the depth records of the other.Burgess
pp. 320–321.

Death

Exley died, aged 45, on April 6, 1994 while attempting to descend to a depth of over in a freshwater

, or sinkhole, called Zacatón in the state of

Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...

, Mexico. He made the dive as part of a dual dive with Jim Bowden, but Bowden aborted his descent early when his gas supply ran low. Exley's body was recovered when his support crew hauled up his unused decompression tanks. It was found that he had looped into the descent line, perhaps to sort out gas issues. His wrist-mounted dive computer read a maximum depth of . The cause of Exley's death could not be determined. Team members concluded the causes "...could include stress of HPNS exacerbated by the

narcotic The term narcotic (, from ancient Greek ναρκῶ ''narkō'', "to make numb") originally referred medically to any psychoactive compound with numbing or paralyzing properties. In the United States, it has since become associated with opiates ...

effects of nitrogen at that depth". The line was also wrapped (deliberately) around Exley's tank valves. Bowden and other experts have theorized that Exley might have done this in anticipation of his own death to prevent any dangerous body recovery operations. The

remipede Remipedia is a class of blind crustaceans found in coastal aquifers which contain saline groundwater, with populations identified in almost every ocean basin so far explored, including in Australia, the Caribbean Sea, and the Atlantic Ocean. The ...

''L. exleyi'', discovered by Australian cave divers Andrew Poole and Dave Warren in August 1993, was named in honor of Sheck Exley.

Books

* Mapping Underwater Caves. National Association for Cave Diving. 1973, coauthored with Bob Friedman * Basic Cave Diving: A Blueprint for Survival. Cave Diving Section of the

, 1979. * Caverns Measureless to Man. , Cave Books, 1994. * The Taming of the Slough: A Comprehensive History of Peacock Springs. , National Speleological Society, 2004.

References

External links