“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.”