TO a man, the crew of the Nimrod rescue aircraft quietly urged the fisherman on as they watched him painfully inch his way towards the liferaft they had dropped.

With a superhuman effort, the survivor, who had been in the stormy Atlantic ocean for more than 12 hours, fought his way out of the water and into the shelter of the raft.

Hopes of finding alive any more of the crew of the sunken German trawler Hansa had been fading fast when a man in an orange immersion suit was spotted waving to them from the water.

The Nimrod long-range search and reconnaissance aircraft then dropped two liferafts, linked by 400ft of rope, upwind of the man.

Flight Lieutenant Steve James, the pilot, said: ''First we saw him get hold of the rope, and again give us a wave.

''Then he began slowly pulling himself along it towards one of the rafts. We were not yelling 'Go on my son,' but I think that inside we were all thinking it.

''We were willing him to make it along that rope and get into that dinghy so that he would soon be in safe hands. It probably took him 10 minutes longer to reach the raft and then clamber in.

''What that guy did was superhuman and I think it was a tremendous will to survive that kept him going.''

Experts said yesterday that the fisherman owed his life in large part to the immersion suit he was wearing, without which he would have been lucky to survive an hour.

Another factor was that the water was warmed by the gulf stream to 10C, yet still 27C below normal body temperature.

It is virtually certain that he was wearing an insulated suit, the type favoured by Germans, which are designed to slow down the loss of body heat. Dave Parslow, marketing manager of International Safety Products, which manufactures immersion suits and other safety equipment, said: ''My hunch is that if he was wearing one of the German-type suits, it will have had a splash guard which covers the mouth when the face is sealed.

''A lot of drownings in these circumstances are caused because people become so tired they simply lose the ability to spit.''

The man's metabolism will also have been in major factor in his survival, as will his physical make-up. Large people with a lot of body fat have been known to survive much longer than thin people in cold water, providing they survive the initial immersion.

Mr Parslow said statistics suggested that, after six hours in water of 10C, only around 10% of people who took to the water in immersion suits would be expected to survive, and that fell to 5% in water of 5C.

Ian Cullen, director of a safety training centre in Tyne and Wear, said there were many factors determining survival time, including the number of people stranded together.

''Several people together in the water would usually stand a better chance of survival than someone by himself,'' he said.

''Two or three people can support each other psychologically, and physically, and also act as a bigger target for rescue teams flying overhead.

''The fact that one person by himself has survived and been picked out of the water is a truly remarkable feat.''

Meanwhile, it emerged that the crew of the stricken trawler did not manage to send a proper Mayday signal when it went down on Monday night.

The Hansa distress call was weak when sent out before 11pm and there was no further response when coastguards tried to contact the vessel.

In the past, such failures have been explained by the radio aerial being below the water, either because the aerial has broken or the vessel has turned turtle, according to Annette McHugh, deputy watch manager at Solent coastguard station.

Great escapes

In 1997, Tony Bullimore, the round-the-world yachtsman, spent 90 hours in the freezing hull of his upturned boat 1200 miles from the Australian coast. By the time a rescue vessel reached him four days later, he had only 24 hours of oxygen left.

A 13-month-old Canadian girl, dubbed the miracle baby, last month survived several hours outdoors in sub-zero temperatures. The girl, clad only in a nappy, was found lying in the snow with her toes frozen together and her mouth frozen shut.

A brother and sister astonished rescuers who found them trapped in their kitchen in Bhuj, 10 days after India's worst earthquake struck last month. They were discovered moments before the army was due to bring in bulldozers to raze the damaged buildings around them.

One of the most famous survival stories is that of the team of amateur rugby players from Uruguay whose plane crashed in the remote Andes in 1972. Those who survived did so by becoming cannibals.