It looked like a normal day's fishing for the Maria Delia. The Mexican trawlerA boat that pulls a large net to catch fish. had set off in search of tuna when the helicopter helping it scout the seas radioed an extraordinary report. It had spotted a damaged catamaranA type of boat with two parallel hulls. far from land. On board was a wild-looking man and the only member of his crew: his pet dog.

Tim Shaddock had set out from the Mexican port of La Paz in April, hoping to reach French PolynesiaA group of more than 100 islands in the Pacific which are attached to France. . But not long after the start of his voyage his boat hit a storm which put its electronics and communication equipment out of action.

Shaddock survived by catching fish which he ate raw, drinking rainwater and sheltering from the sun under a canopy. After picking him up last Wednesday, the trawler took him back to Mexico.

According to Mike Tipton, a professor of physiologyThe study of how the human body works. at Portsmouth University, his survival was down to a mixture of luck and skill. He was lucky that there was enough rain to provide the water he needed, but skilful in catching fish and rationing it carefully.

According to Guinness World Records, the longest anyone has survived at sea is 484 days. In October 1813 a ship was damaged by a storm off the Japanese coast and drifted in the Pacific until spotted in March 1815. Luckily it had a cargo of soy beans that the crew could eat, but 12 of the 14 men on board died of scurvyA disease caused by a lack of Vitamin C - most often caused by not eating enough fruits or vegetables. .

During World War Two, a Chinese sailor from a British merchant vessel that had been torpedoed survived on a life raft for 133 days. At one point he caught a shark and drank its blood to keep him going.

It is generally agreed that mental attitude is a vital factor in surviving. Professor Tipton believes that having his dog Bella as a companion helped Tim Shaddock "a tremendous amount."

Some believe that ultimately it all comes down to willpower. According to one expert, Nick Vroomans, "I've known of people who have been in a perfectly survivable situation who have basically thrown it away and given up... while other people have just persevered with very little knowledge but have been able to tough it out mentally, so the will to live is key."

But writing in Huffington Post, Dr Ali Binazir argues that there is no such thing as willpower. Instead, he says, the way to survive and flourish is by creating the right conditions for yourself.

Yes: In 2012 two Mexicans were left helpless in a storm-damaged boat. After four months one gave up, stopped eating and died. The other had the will to keep going for another 10 months and survived.

No: There is no actual evidence that it exists. According to Dr Binazir, you do not resist temptation by willpower, but by keeping away from the things that tempt you.

Or... Survival in these accounts has been attributed to willpower, luck and skill. The only one whose existence everyone can agree on is skill - so that must be the most important of the three.