I don’t know of any sport where the goalposts can shift the way they do with endurance swimming. - Lewis Pugh

A massive turquoise glacier feeds into Magdalenefjord, with chunks of ice as big as buildings breaking off and landing in the water to float away as icebergs. As I swam past them, with my head in the water, I heard a tantalising sound: a snap-crackle-pop, just like Rice Krispies in milk. It was the sound of tiny air bubbles being released from the ice – air that had been trapped there as much as 3,000 years ago. To swim through this sound, I thought, is to swim in history.

When people say to me, you must have a very strong mind to swim across the North Pole, or off Antarctica or on Mount Everest, I tell them that endurance swimming builds good mental strength.

As a pioneer swimmer, you've got to be willing to fail and try again. The point isn’t to learn to fail, the point is to learn to bounce back.