Diving is deep-sea commercial diving in which the diver's bloodstream is
saturated with a mixture of helium and oxygen equalised to the same pressure of
the surrounding water, so that the decompression time following the dive is
independent of the duration of the dive itself. This enables the divers to live
in a saturation diving chamber located within a Diving Support Vessel. The
following videos give a very good explanation of how Saturation Diving took
place then and now, and the dangers involved and associated with
commercial saturation diving.
the mid 1970's commercial diving was a necessity to bring oil ashore once it
had been discovered in the North Sea. Pipelines would run from rigs to shore
and divers were required to assemble both the subsea installations and
pipelines themselves. It was a requirement for commercial divers to live
at the same pressure as that in which they were working.
Saturation diving was seen as the best way to safely enable them to work
at such depths for long periods of time. Otherwise divers would need to
re-compress after each dive, a long drawn-out process
requiring many divers to do the work.