Saturation diving involves diving for long periods of time. It is considered to be one of the most dangerous and isolating professions.

Divers often spend weeks in a constant state of pressure because of how deep they are. They will spend weeks living onboard a ship inside a pressurized chamber that allows the divers to acclimatize themselves to the conditions.

Duncan Allcock, David Yuasa, and Chris Lemons are members of a team of saturation divers who work to maintain undersea gas lines in the North Sea. In 2012, while David and Chris were several hundred feet below the ocean's surface, a failure occurred in the team's support vessel. The vessel's dynamic positioning system ended up failing and causing it to drift away from the work area.

The drift ended up dragging the divers away. David was able to get himself back to the diving bell, but the force from the drag eventually snapped Chris' umbilical tether. The tether was supplying the divers with heliox to breathe, as well as hot water to heat the suits, power for their lights, and a communications link with the surface.

Without his tether, Chris was left with only five minutes of breathable gas contained in the cylinders he wore on his back.

By a miracle, Chris managed to find his way back to the work area and climb onto the structure, where he eventually passed out. After several near misses, Duncan and David were able to locate Chris and get him back aboard the ship. Chris would regain consciousness in the diving bell after some assisted breaths from Duncan.

Though nobody knows exactly how Chris ended up surviving for around 30 minutes. A leading theory in Chris' survival is that the cold water mixed with having been breathing a gas mix with a high partial pressure of oxygen. After the incident, Chris was back to work just three weeks later to finish the job.

This story was brought to the public's attention in the 2019 documentary titled Last Breath. It was directed by Richard da Costa and Alex Parkinson and uses genuine footage and audio recorded at the time of the accident via the divers' radios and body cameras. The film was also supplemented with interviews of several of the individuals involved.

Parkinson would go on to direct a feature film version of the event, with the same title, Last Breath. The film starred Woody Harrelson as Duncan, Simu Liu as David, and Finn Cole as Chris. It was released on Feb. 28, 2025. ~Ryan Donahue