Big Man of the River prepares to swim the full length of the Amazon - or 'die trying'

A middle-aged man with the physique of a bear slipped into the warm water of the Amazon river yesterday to begin the longest and probably most dangerous swim ever attempted.

Martin Strel, from Slovenia, known variously as "Big Man of the River" and "Fish Man", is attempting to swim the full length of the world's longest river - all 3,375 miles (5,400km) of it - or, in his own words, "die trying".

As a marathon swimmer, he is no stranger to staggering feats of endurance. After conquering the English Channel early in his career he has gone on to swim the length of the Danube, Mississippi and Yangtze rivers. None of them, however, compares with the terrors waiting for him in the Amazon: anacondas, crocodiles, poisonous freshwater stingrays and even the occasional bull shark that works its way upstream.

But Strel, 52, remains philosophical: "I'm concerned, of course, but if I think of that stuff I would never jump into the water," he told reporters. He even had a ready reply when asked about every man's greatest fear in the equatorial waters - the toothpick fish that can enter the body by swimming up the penis, and can only be removed by surgery. "I never urinate straight into the water, I always urinate straight into my wetsuit," he said.

Yesterday's starting point was Atalaya in Peru, from where Strel will attempt to make it to where the river spills out of the Amazon Basin into the Atlantic, at Belem. His first challenge will be ferocious local whirlpools that have sunk passenger ships.

The world record distance swimmer intends to get there in 70 days, which means swimming from dusk to dawn, to clock up the necessary 48 miles a day. He will be accompanied by 45 people in three boats including a doctor and trainers. The main vessel in the $1m (£51m) mission belonged to the oceanographer Jacques Cousteau.

The team will be carrying buckets of animal blood to distract predators as a first line of defence. If that doesn't work there will be armed personnel in the support flotilla. And if the attackers still make it through, the medical team have a couple of pints of Mr Strel's own blood in reserve for emergencies.

With the promise of dramatic encounters and human triumph there is of course a US documentary team accompanying which is recording the feat for a film called Big River Man.

While admitting that his effort appears to defy logic, the veteran peace campaigner insists that his goal is "to show that nothing is impossible". A national hero in his native Slovenia, where schoolchildren are taught his life story among those of six great Slovenians, Strel attributes his toughness to a harsh upbringing. He said: "As a boy, I was beaten a lot by my parents and schoolmasters. This no doubt contributed greatly to my ability to ignore pain and endure."

His current best performance is 2,360 miles (3,776km) in 68 days, a feat he achieved by conquering the Mississippi. But before he gets that far he will have to contend with the Pororoca, a massive tidal bore that reaches four metres high and has started a craze for Amazon river surfing. "It is very dangerous," Strel said. "It is great for surfing but bad for swimmers,"