You're never too old to really test those physical limits. Well, when you do get to Diana Nyad's 64 years of age, maybe it'd be for the best if you go a little easier on yourself. Nyad made history by being the first person to make the 110-mile swim from Havana to Key West without the protective aid of a shark cage. It was her fifth attempt at the feat (her first try came in 1978), and her first that ended in success. The 53-hour swim was a grueling lesson in utterly insane perseverance, as she recalled stroking through throngs of stinging jellyfish at one point and vomiting from having too much saltwater in her system at another, among other things. But in the end, she was able to carry out her mantra, "Find a way."