Okene had absorbed nitrogen at approximately four atmospheres of pressure for more than sixty hours. His tissues were saturated with dissolved nitrogen in a way that no diver following standard protocols would allow to develop. Bringing him directly to the surface — an ascent from 30 meters in a matter of minutes — would almost certainly have killed him or left him severely disabled.
Chamberlain has described what the divers told Okene about nitrogen: that the buildup in his tissues, if not properly managed, could cause a heart attack during or after ascent. Whether Okene fully understood the physiological mechanism is less important than the fact that he submitted to the controlled process rather than trying to ascend on his own.
The process of extracting Okene from the wreck and managing his decompression required fitting him with diving equipment — gear he had never used and had to be taught to use, underwater, by the rescue divers. He was equipped with a diving helmet and breathing apparatus, moved through the wreck to a diving bell, and transferred under controlled pressure conditions to the surface. The diving bell maintained the pressure of the depth during the ascent, preserving the pressure differential that the decompression schedule required.
Once on the support vessel at the surface, he was placed in a hyperbaric chamber — a decompression chamber that maintains elevated pressure and then slowly brings it down according to a medical schedule designed to allow dissolved nitrogen to exit the tissues slowly enough to prevent bubble formation. He spent approximately two and a half days in the chamber before it was safe to bring him to normal atmospheric pressure.