Lewis Pugh at TEDGlobal 2010

Lewis Pugh's mind-shifting Mt. Everest swim : After he swam the North Pole, Lewis Pugh vowed never to take another cold-water dip. Then, he heard of Mt. Everest's Lake Imja -- a body of water at an altitude of 5,300 meters, entirely created by recent glacial melting -- and began a journey that would teach him a radical new way to approach both swimming and think about climate change.