In a chilling tale, a catastrophic error which took place below the ocean’s surface led to what have been dubbed some of the ‘most gruesome deaths’ in history, claiming the lives of five out of six men involved.

The horrifying incident unfolded on a semi-submersible oil drilling rig where the divers were assigned to carry out a deep-sea diving mission. Although the rig appeared unremarkable, it was sadly the scene of numerous accidents involving its workers during its operational years.

One such dreadful accident transpired on the rig in 1983.

The terrifying tragedy of 1983

The Byford Dolphin, a semi-submersible oil drilling rig, operated across the British, Norwegian, and Danish sectors in the North Sea, conducting seasonal drilling for various companies.

In November 1983, a team comprising two British and two Norwegian divers — Roy P Lucas, 38, Edwin Arthur Coward, 35, Truls Hellevik, 34, and Bjørn Giaever Bergersen, 29 — along with dive tenders William Crammond, 32, and Martin Saunders, 30, were stationed on the rig to undertake a deep-sea diving mission.

At the time of the incident, all six men were performing their duties underwater, conducting routine maintenance on the rig at an astounding depth of 295 feet. To safely carry out their tasks, the crew were housed in special compression chambers for their planned 28-day stint to prevent excessive nitrogen build-up in their bloodstreams.

Inside these chambers, the divers would breathe a carefully measured blend of gases, typically oxygen and helium, adjusted according to the depth of their dive.

The team utilised a technique known as ‘saturation diving’, which enabled them to spend prolonged periods at significant depths underwater. This method was employed to ensure the crew could avoid decompression sickness, commonly known as ‘the bends’, when they ascended to the surface.

The men used a specialised transport vessel, a diving bell, to safely commute between their living quarters and their underwater work site.

On 5 November 1983, divers Hellevik and Bergersen were finishing a 12-hour shift, aided by dive tenders Saunders and Crammond. They were returning to their sleeping quarters using the diving bell.

For the safe operation of the diving bell, it was crucial that the crew ensured the transportation vessel was sealed and correctly reconnected before they returned to their highly pressurised sleeping chambers. This procedure was necessary to prevent rapid decompression in the body, which could be lethal.

Once inside, the divers had to close the door and adjust the pressure in their sleeping chamber to create an airtight seal. This action would then isolate the chamber and connect it to the dive bell, which would gradually depressurise for the safety of the divers.

However, on that ill-fated day, the pressure in the inner crew chambers 1 and 2 (usually pressurised to nine atmospheres) plummeted to one atmosphere within a fraction of a second. This happened because one of the external divers made a human error and unlatched the diving bell prematurely before complete depressurisation had occurred.

This mistake caused the clamp – which was keeping the chambers sealed – to open before Hellevik had fully closed the chamber door. As a result, the pressure in the sleeping chamber abruptly changed from that found at 295 feet underwater to surface air pressure, reports the Mirror.

Coward and Lucas were reportedly resting in chamber 2, under a pressure of 9 atmospheres when the tragic incident occurred. The sudden, forceful rush of air exiting the chamber caused the diving bell to be violently propelled, striking Crammond and killing him instantly.

It is believed that three divers inside the sleeping chambers died immediately as the nitrogen in their blood turned into bubbles, effectively boiling them from within and reducing their bodies to countless fragments.

Hellevik, who was nearest to the partially closed chamber door, was sucked through a small 60cm gap, resulting in his organs being ejected from his body. The autopsy report stated: “The scalp with long, blond hair was present, but the top of the skull and the brain were missing. The soft tissues of the face were found, however, completely separated from the bones.”

His is abdominal and thoracic organs had been expelled. Hellevik’s body was reportedly sent for autopsy in four separate bags collected from various locations around the rig. Each part of his body inside the bags of bone and tissue reportedly displayed some sign of injury.

Saunders, the only survivor of the horrific accident, sustained severe injuries including collapsed lungs, back fractures and a broken neck.

The fatal event was also linked to engineering failures. The Byford Dolphin oil rig was using an outdated diving system from 1975, lacking fail-safe hatches, outboard pressure gauges or an interlocking mechanism.

This crucial feature would have prevented the divers’ sleeping chambers from opening while the system was pressurised. Despite these shortcomings, the Byford Dolphin oil rig continued operations with upgrades and changed hands until it was finally decommissioned in 2019.

It was eventually sold for demolition in the 2020s.