What does it feel like to stand on the edge of the sea ice at the North Pole in nothing more than a Speedo swimming costume? What kind of man dives into that freezing ocean and swims a full kilometre? And why? The intrepid environmentalist, endurance swimmer and inspirational UN Patron of the Oceans has swum as far north and as far south as a body can get, as well as on the earth's highest mountain. He's learned a few things about the extremes of human nature, and our fragile blue planet, along the way. Chaired by Paul Blezard.