It’s a story that almost defies belief: A man leaves Mexico in December 2012 for a day of shark fishing and ends up surviving 13 months on fish, birds, and turtles before washing ashore on the remote Marshall Islands 8,800km away.

An emaciated man whose boat washed up on a remote Pacific atoll this week claims he survived 16 months adrift, floating more than 12,500km from Mexico, a researcher said.