Deep diving...
Has different meanings depending on the context. Even in recreational diving the meaning may
vary:
In recreational diving, a depth below about 30 metres (98 ft), where nitrogen narcosis becomes a
significant hazard for some divers, may be considered a "deep dive".
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 metres (60 ft) to 30 metres (100 ft) as a "deep dive" in the context of recreational
diving (other diving organisations vary), and considers deep diving a form of technical diving.
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".
Deep diving can mean something else in the commercial diving field. For instance early
experiments carried out by Comex S.A. (Compagnie maritime d'expertises) using hydrox and
trimix attained far greater depths than any recreational technical diving. One example being the
Comex Janus IV open-sea dive to 501 metres (1,644 ft) in 1977. The open-sea diving depth record
was achieved in 1988 by a team of Comex divers who performed pipeline connection exercises at a
depth of 534 metres (1,752 ft) in the Mediterranean Sea as part of the Hydra 8 programme. These
divers needed to breathe special gas mixtures because they were exposed to very high ambient
pressure (more than 50 times atmospheric pressure).
An atmospheric diving suit allows very deep dives of up to 700 metres (2,300 ft). 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 high pressure gases.