Climate change is the Everest of all problems, the thorniest challenge facing humankind.
Lewis Gordon Pugh
Of all the creatures in the world that really frighten me - the hyena in Africa, the great white shark - leopard seals are near the top of the list. They're killers. If my team spots one, they'll pull me out of the water.
I wish politicians would put the environment at the centre of every agenda.
Britain has bred many great explorers, but they seem to get so little coverage compared to soccer and rugby players.
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.
Not to be too grandiose about it, but in a way I see myself like Sir Edmund Hillary. The water was my Everest.
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.
I've been on swims where people have freaked out about sharks. You have to think about something else, otherwise it will absolutely paralyze you. I do math problems, anything.
When I'm preparing for a swim, I imagine absolutely everything about it: the color of the water, how cold it is, the taste of salt in my mouth. I visualize each and every stroke.
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.
The swim at Deception Island was by far the hardest swim I've ever done. Antarctica is a very unforgiving environment. If you don't train properly, you'll die.
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.
On 15 July 2007, I swam across an open patch of sea at the North Pole to highlight the melting of the Arctic sea ice.
I learned two basic lessons on Everest. First, just because something has worked in the past does not mean it will work today. Second, different challenges require different mindsets.
Normally I don't race other people; I challenge the environment and my own limitations.
The days of exploration of Shackleton and Scott are long gone. Everything has been climbed, crossed, done. Now what we're exploring are the full boundaries of human endeavour. It's not physical - it's all in the head.
Swimming has been a very effective medium for telling a story about the state of our planet.
The human body is not designed for swimming in minus 1.7 degree centigrade water.
I just never, ever want to give up. Most battles are won in the 11th hour, and most people give up. If you give up once, it's quite hard. If you give up a second time, it's a little bit easier. Give up a third time, it's starting to become a habit.
The problem with climate change is that it's quite complicated for the ordinary person to understand.
We need to save the Arctic not because of the polar bears, and not because it is the most beautiful place in the world, but because our very survival depends upon it.
I can't think of anything more important than the environment we leave to our children and our children's children.
