Lewis Pugh was never afraid to take the plunge. Now ocean advocate for the United Nations Environment Programme, the record-breaking cold-water swimmer has completed long distance swims at both of the earth's Poles, in the Red Sea, and along the length of the Hudson River, to spread a message of habitat renewal and conservation.

"The first thing that happens is I can't breathe and I'm gasping for air. And the cold just grips its way around you. And you just got to try and control your mind, because there's a moment when you feel like panicking because there's nothing like this."

Healthy oceans, seas and rivers are essential to supporting life on Earth - providing food, medicine, and acting as the world's largest carbon sink. In this episode, Lewis Pugh reflects on his love for the water, on his breathtaking swims, and on breaking the diplomatic ice to create the world's largest marine park.