Lewis Pugh: The world's leading cold-water swimmer on pain, the plight of the penguins and taking time over tea

Pugh swimming the Thames in 2006 (Getty Images)

As a young boy I saw myself as Sir Edmund Hillary, and water as my Everest When Hillary and Tenzing Norgay walked up Everest, they didn't know whether they would be coming down again; it's a pioneer mindset. Similarly, as a cold-water swimmer, standing on the edge of the sea ice as you're about to dive into the black water is terrifying: I don't know what will happen by the end of the swim – or even if I will still be alive.

There's a huge difference between swimming in Antarctica and the North Pole The English Channel today is about 18C, while the passengers of the Titanic perished in the Atlantic at 5C. I did a swim off Antarctica, in 2005, and the water there was zero degrees –and it was cold. But when I swam in an open patch of sea in the North Pole, at -1.7C, the difference was extraordinary: I'm the only person in world who can do that [thanks to an ability to increase his core temperature to 38C]. But my whole body was in pain and I was gasping for air.

The Titanic's Passengers didn't die from the cold They drowned from hyperventilating from the shock of being in cold water. You have to control your breathing and focus on what it is you want to do.

To get your mind right you need to have really powerful music Before a swim I try to listen to something rousing, such as Verdi's "Chorus of the Hebrew Slaves", but Puff Daddy does it for me, too.

I think white South Africans have a huge sense now of right and wrong It's because of what happened under Apartheid. I moved there from the UK when I was 10; growing up, all around me people fighting for human rights were going to jail, even dying. So now, if I see an injustice happening, I feel I have a moral obligation to stand up and serve for a greater purpose.

When we protect our environment, we bring peace When I left South Africa [to work as a maritime lawyer, in London], the person who came down to the beach to see me off was Desmond Tutu. He said, "Lewis, when we damage our environment and don't protect our resources, we create conditions ripe for conflict. You are a peace campaigner, God bless you and go for it." That's Tutu the Nobel Laureate; it was powerful stuff and I felt it gave me a purpose: to draw attention to what's happening in our oceans.

Wherever I go in the ocean, I see overfishing and pollution My first long-distance swim, from Robben Island to Cape Town, I did in 1987, and I remember having lots of African penguins darting and swimming underneath me, which was a wonderful feeling. I did the swim again recently and didn't see one penguin; penguin numbers are down from four million in 1900 to 60,000 now.

I have to keep all my windows open at home Some people like to sleep and be all toasty. I like to be all toasty under the duvet, too, but I like my face to be freezing, as I like to be exposed to the fresh air. Unfortunately, my wife hates it; she thinks it's my worst habit.

I love how the Nepalese take their time over tea When you spend time in Nepal you realise how much people enjoy sharing a cup of tea; they don't slap together a builder's and polish it off, they take their time pouring it out and drinking it, as their tea is very much a coming together of people.

Lewis Pugh, 44, is a maritime lawyer and the only cold-water swimmer to have completed a long-distance swim in every ocean. You can follow Pugh's attempt to swim the world's seven seas at lewispugh.com