Sport on TV: Barrel-bellied man floats down in a stream of unconsciousness

When it comes to extreme feats of physical endurance, it's debatable whether they should be shown on TV.

There is an inevitable blurring of the boundaries between reality and fantasy, and copycats may put themselves in grave danger. But few are likely to follow in the wake of Martin Strel, an overweight 53-year-old, in Big River Man (More 4, Tuesday) who swam the whole of the Amazon while drinking two bottles of wine a day.

Here is a man who probably could have drunk the Amazon, let alone swum it. According to his son Borut, Strel is "the ambassador of Slovenia" and a national hero, which is hardly surprising since, as Borut said: "We are top in Europe for drunk-drivers". But there is more to Strel than boozing. He eats horses, gambles heavily, stars in films, meets heads of state, judges beauty contests and, when he is not swimming the Mississippi or the Yangtze, he teaches flamenco guitar.

The Yangtze is the filthiest river in the world, and Strel also acts as a rather slurred spokesman for cleaning up the world's most polluted waterways. In the 59 days it took to tame the Yangtze, he had to have his blood washed every day because he kept having to swim past dead bodies.

The Amazon is 1,000km longer and his navigator, Matt, a supermarket worker from Wisconsin, has no idea about navigation. Then Matt seems to lose his mind, jabbering about how Strel is "almost Christ-like, the last superhero in the world". That would be one hell of a world.

This two-hour film, which was warmly received at Cannes last year, soon starts to feel like an Apocalypse Now journey into the depths of the human soul. Strel even looks like a hybrid of Marlon Brando and Dennis Hopper.

Fact and fantasy merge for the protagonists as well as the viewers. It's like a prehistoric world; Indian tribes offer him potions which, of course, he guzzles down and he starts to hear voices and hallucinate when he gets a larval infection in his head. But he still swims 60 miles a day for 75 days.

Two weeks ago we had Wild Swimming with Dr Alice Roberts, celebrating the sense of freedom that comes with jumping in your nearest river. This is a whole different kettle of fish. "He was beaten very badly as a child," says Borut. "That is why he can endure such extreme pain. That is why he battles demons in the rivers." Strel learned to swim long distances when trying to get away from his father, who was pursuing him down a riverbank. He kept going until his father gave up and went home. On the surface he is a rotund figure of fun but for Strel the waters run deep.

Even his own son did not know about this anecdote until Martin confided in him after imbibing an Amazonian potion. It's difficult to know what is fact and what is fiction here, but when it comes to creating a mythology, that comes with the territory.