The human body is not designed for swimming in minus 1.7 degree centigrade water.

When I was born, the world's population was 3.5 billion. There are now 6.8 billion people on the planet. By 2050, that's expected to rise to 9.4 billion. What's more, the Earth's resources aren't growing; they're decreasing - and rapidly.

Swimming has been a very effective medium for telling a story about the state of our planet.

I wish politicians would put the environment at the centre of every agenda.

In the cold, all the blood rushes to your core to protect your heart, lungs, kidneys, liver, and brain. When you leave the water, the blood rushes back to your arms and legs, absorbs that freezing cold, and brings it back to the heart.

I think that I was slightly naive. I thought that if I showed people the beauty of the Arctic and the beauty of the polar bears that they would care so much that they would stand up and try to make a change.

Normally I don't race other people; I challenge the environment and my own limitations.

I can't think of anything more important than the environment we leave to our children and our children's children.

Britain has bred many great explorers, but they seem to get so little coverage compared to soccer and rugby players.

On my second swim at Deception Island, the water was very clear and I was looking at hundreds of whale bones beneath me. It was a graveyard from the whaling some time in the 1920s-30s.