Hof began a lifelong quest to see just how far his abilities would take him. In January of 1999 he traveled 100 miles north of the Arctic Circle to run a half-marathon in his bare feet. Three years later, dressed only in a swimsuit, he dove under the ice at the North Pole and earned a Guinness World Record for the longest amount of time swimming under the ice: 80 meters, almost twice the length of an Olympic-sized pool.