Saturation diving is a method of diving for long periods of time to reduce the number of decompressions the divers must go through when working on long dives or dives at great depths. Because of the pressurized gases used when diving to dilute the oxygen to non-toxic levels, returning to the surface safely requires a very strict procedure to ensure the diver's safety. The build-up of gasses like nitrogen in the body can result in ins some very serious and even fatal issues if not done correctly.

This is exactly what happened at the Byford Dolphin, a semi-submersible, column-stabilized drilling rig that had several incidents but most notably an explosive decompression in 1983 that killed four divers and one dive tender, and badly injured another dive tender.

It's a long story and a horrible one. It's about a super deep saturation dive gone wrong. The Byford Dolphin accident is one of the most terrible accidents in recent history.

The 4 divers who were inside the decompression chamber that fateful day could not even realize what had happened, as they died in a fraction of a second.

This is the most brutal, painless death in history.

It's a long one so if you want the nitty gritty, skip to @6:35.