‘The director John Maringouin first contacted me and my son Borut in 2002 after John’s wife Molly had seen a report on CNN about me swimming the Mississippi. When they found out that I was planning to swim the Amazon in 2007 to raise environmental awareness, they asked us if they could make a documentary about the adventure. We looked at John’s past work, including his documentary Running Stumbled, and realised that he was drawn to extreme characters. He came and filmed me in Slovenia before the swim and I trusted him.

‘To cover the whole of the Amazon, which stretches over 3200 miles, I swam for 70 days, spending 10-12 hours a day in the water. It’s incredibly dangerous swimming there. You can’t see below the surface of the muddy water, and you’re exposed to the sun all day. I caught dengue fever and parasites burrowed underneath my skin. My medical team was always busy. There’s also the risk of pirates, and some of the tribe’s people thought I was a demon and threatened to kill me unless I left. And it’s not just a question of physical strength – it’s a test of your mind, because every stroke could be your last. I don’t think the Amazon is a place for Europeans to live, it’s for the indigenous peoples. We had no editing rights on the film. We had to wait 18 months until the world premiere at Sundance in January 2009, before we could see the completed film. If I had known how I would be portrayed in Big River Man, I’m not sure that I would have signed up with John. I think the film makes me out to be some sort of crazy man and an alcoholic, and I regard myself as an athlete, and as somebody who likes to drink wine. Obviously we don’t have a chance to do the trip again with a different film crew. The most important thing though is that the Amazon swim changed my life. For me it was like climbing Mount Everest. Part of me still feels I’m in the jungle or the water.’

Big River Man is available on DVD from Mon 18 Jan (Revolver)