In May 2013, the tugboat Jascon-4 flipped in rough seas off Nigeria. It sank upside down to the sea floor, 30 metres down. Like air in a cup pushed upside down into water, some air stayed trapped inside.
The cook, Harrison Okene, felt his way underwater into the engineer's office, where an air pocket about 1.2 metres high kept him alive.
Sixty hours later, divers who came to recover bodies found him alive.