On Saturday, 5 November 1983 at 4:00 a.m., while drilling in the Frigg gas field in the Norwegian sector of the North Sea, four divers were in a diving chamber system on the rig's deck that was connected by a trunk (a short passage) to a diving bell. The divers were Edwin Arthur Coward (British, 35 years old), Roy P. Lucas (British, 38), Bjrn Giver Bergersen (Norwegian, 29) and Truls Hellevik (Norwegian, 34). They were assisted by two dive tenders, William Brown Crammond and Martin Andrew Saunders.[6]
Hellevik was about to close the door between the chamber system and the trunk when the chamber explosively decompressed from a pressure of nine atmospheres to one atmosphere. One of the tenders, 32-year-old William Crammond of Great Britain, and all four of the divers were killed instantly; the other tender, Saunders, was severely injured.[10]
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Medical investigations were carried out on the remains of the four divers and of one of the tenders. The most notable finding was the presence of large amounts of fat in large arteries and veins and in the cardiac chambers, as well as intravascular fat in organs, especially the liver.[6]:97, 101 This fat was unlikely to be embolic, but must have precipitated from the blood in situ.[6]:101 The autopsy suggested that rapid bubble formation in the blood denatured the lipoprotein complexes, rendering the lipids insoluble.[6]:101 The blood of the three divers left intact inside the chambers likely boiled instantly, stopping their circulation.[6]:101 The fourth diver was dismembered and mutilated by the blast forcing him out through the partially blocked doorway and would have died instantly.[6]:95, 100101
Coward, Lucas, and Bergersen were exposed to the effects of explosive decompression and died in the positions indicated by the diagram. Investigation by forensic pathologists determined that Hellevik, being exposed to the highest pressure gradient and in the process of moving to secure the inner door, was forced through the 60-centimetre (24 in) diameter opening created by the jammed interior trunk door by escaping air and violently dismembered, including bisection of his thoracoabdominal cavity, which resulted in expulsion of all of the internal organs of his chest and abdomen, except the trachea and a section of small intestine, and of the thoracic spine. These were projected some distance, one section being found 10 metres (30 ft) vertically above the exterior pressure door.[6]:95
tl;dr: three of the guys' blood boiled, and the other one was sucked through a two foot diameter opening, ripping apart his abdomen, then throwing all his internal organs and part of his spine all over the decompression chamber. (The other three would have stayed alive for a while while they boiled and would have seen all this.)