MSN – story by Jess Thomson

On May 23, it will be 10 years since a man named Harrison Okene survived three days at the bottom of the sea in the wreck of a ship.

The 29-year-old had been trapped in the freezing cold and pitch-black darkness 100 feet beneath the ocean surface for 60 hours. He is believed to have been just hours from death when he was found.

“It was very unexpected and a total shock to find someone alive after the vessel sank days before,” Nico van Heerden, the diver who found Okene, told Newsweek. “He was not the first person we came across, though. Before we found him, we found and recovered the bodies of three of his colleagues that perished during the incident. Very tragic indeed.”

He went on: “Vessels do sink and people die, but to find someone alive after so long does not happen. I’ve never heard of it happening before.”

Okene was a cook on a tugboat named the Jascon-4. The small boat was on its way to a nearby oil tanker, about 19 miles off the west coast of Nigeria, when a large wave suddenly capsized the vessel.

“Before we knew, we were sinking,” Okene told Nine News Australia. “We had been sailing for many years, we knew the sea, we had never had any issue before.”

Okene began rushing through the ship but found many of the doors were locked to prevent pirates from entering. He became trapped inside a toilet in the officers’ cabins as water poured into the ship and could not escape as the ship began to sink to the bottom of the sea.

By some stroke of luck, an air pocket stayed intact inside the toilet. He could breathe but was in total darkness and aching cold. “Underwater it was so, so, so, cold,” he said. “I was struggling to stay alive, wondering how long [the air pocket] would last me. I was thinking about my family, my wife, what would happen, how would she live, how can I get out, thinking about my life as well.”

Okene tried to find his way out of the underwater maze but to no avail, using a rope to find his way back to his air pocket when he ran out of breath. “I was praying a lot,” he said.

Being trapped in the cold in only his underwear, with dwindling air and no food or water, Okene was in huge danger of carbon dioxide toxicity as well as facing thirst, hunger and hypothermia.

“Mr. Okene is lucky to have survived,” Paul Schumacker, a pediatrics professor and hypoxia expert at Northwestern University’s Feinberg School of Medicine, told Newsweek.

He continued: “The temperature of the water at a 30-meter depth can lower one’s body temperature to lethal levels within minutes to hours. Divers always wear insulated suits to retain body heat in cold water. Since he was trapped in an air pocket, it’s possible he was able to lift himself partially out of the water. If only his legs were submerged, this would greatly prolong his ability to maintain body temperature in that environment.”

After approximately 60 hours spent waiting, Okene said, he heard knocking on the side of the boat and saw a beam of light in the darkness. A team of divers had descended 100 feet to the wreck to recover the bodies inside.

Okene reached out and gently tapped one of the divers, van Heerden, on the arm, attempting to not scare him.

“When he came, I was just crying,” Okene said.

At the point he was found, he likely had only a few hours left to live, estimated Eric Hexdall, a nurse and clinical director of diving medicine at the Duke Center for Hyperbaric Medicine and Environmental Physiology.

Hexdall told National Geographic that in an area the size of the air pocket, about 13.5 cubic meters, it takes about 56 hours for carbon dioxide toxicity to set in. Okene had been down there for around 60 hours. It would have taken about 79 hours for him to become unconscious from carbon dioxide, Hexdall said.

“Contrary to popular belief, when people are trapped in confined spaces it is not the oxygen running out that will kill you. It is your own exhaled breath causing a buildup of CO2,” Alex Gibbs, a life support technician on duty on the surface at the time, told Nine News.

He went on: “By the time he had been found, this was at a clearly high level. You can see him panting in the video and his slightly glazed eyes caused by this. We immediately put down an air hose and literally blew fresh air over him. Another concern was he had been saturated by air, so we now had to switch him onto an oxygen and helium mix, which is not standard practice.”

Ten bodies were recovered from the boat during the dive, and one missing person’s body was never found. Okene was the only survivor.

Because of the depth of the wreck, Okene was at risk of decompression sickness, or the bends, if he returned to the surface too quickly, especially with the increased level of nitrogen in his blood from being down so deep for so long. This is a condition often risked by divers and is caused by nitrogen dissolved in the body’s blood and tissues. This can lead to muscle and joint pain, dizziness, paralysis and even death.

“A dive at 30 meters certainly can give you the bends. That is why he was evacuated in a bell, to keep the same pressure and rise it slowly,” Alicia Kowaltowski, a professor of biochemistry at the Universidade de São Paulo in Brazil, told Newsweek.

Okene was guided into the diving bell by the divers before being placed in a decompression chamber at the surface, where he remained for three days.

“At 30 meters depth, the pressure in the air pocket would have been about three times the atmospheric pressure at sea level,” Schumacker said. “Over 60 hours, his body would have absorbed a large quantity of nitrogen gas. Upon return to the surface, it would take hours to exhale all that extra nitrogen gas.”

He continued: “To prevent the gas from forming bubbles in his blood, like you see when opening a bottle of sparkling water, they would need to put him in a hyperbaric chamber pressurized to the same level as in the air pocket. They would then lower the pressure gradually, to allow the trapped nitrogen to be released slowly.”

Despite his ordeal, Okene returned to the depths a few years later. Now a commercial air diver, he worked alongside Gibbs on a diving job last year. He dives to depths of up to 164 feet.

“I’m enjoying diving, it’s life for me, it’s fun,” Okene told Nine News. “I believe the ocean is my world. I feel more comfortable, relaxed there.”

“It’s an incredible rescue, really, and very complicated physiologically,” Kevin Fong, a professor in extreme environment physiology at University College London and a consultant anesthetist, told Newsweek. “Hats off to that team.”