Harrison said he was in the toilet when he realised that the boat was beginning to turn over, and as the vessel sank, he managed to find his way to an area with an air pocket.
"I was there in the water in total darkness just thinking it's the end. I kept thinking the water was going to fill up the room but it did not," he said. "I was so hungry but mostly so, so thirsty. The salt water took the skin off my tongue.
"I could perceive the dead bodies of my crew were nearby. I could smell them. The fish came in and began eating the bodies. I could hear the sound."
But after 60 hours, Harrison heard the sound of knocking.
A team from the DCN global diving company had come to investigate - sent by Chevron and West African Ventures.
"We expected it to be a body recovery job," DCN spokesperson Jed Chamberlain told the BBC's Impact programme.
Harrison "actually grabbed the second diver who went past him", Chamberlain said, giving the diver quite a fright.
Marine and energy industry specialists DCN said the rescue operation involving helicopters and other vessels swung into action almost immediately.
Divers from the firm, whose operations are based in the Netherlands, were working on a project 17 sailing hours away and were eventually ordered to head to the accident site.
"At that time, there was no trace of the crew members ... As internet reports about the accident continued to develop, the realisation grew among the divers that there could still be survivors of the Jascon 4, trapped in an air pocket."
A man who identified himself as Harrison's cousin, Maxwell Ewoma, told AFP that Harrison had been taken to the southern city of Warri.
He said the cook was doing well considering the circumstances and that doctors had ordered him to rest.
"He is doing fine," Ewoma said. "He needs rest. He's still kind of recovering from the shock."
Having been at such depth for so many hours, he needed time in a decompression chamber to normalise his body pressure.
Christine Cridge, a medical director at the Diving Diseases Research Centre, advised the rescue team during this process.
"It's a situation I've not come across before," she told the BBC's Newsday programme.
"After a certain amount of time at pressure, nitrogen will dissolve into the tissues. If he'd ascended directly from 30m to the sea surface ... it's likely he'd have had a cardiac arrest, or at best, serious neurological issues.
Harrison describes his story as a "miracle", but he also told Reuters: "When I am at home sometimes it feels like the bed I am sleeping in is sinking. I think I'm still in the sea again. I jump up and I scream."
