The fearless 60-year-old marathon swimmer, her devoted coach, and the impossible swim from Cuba to Florida — The swim I want to do is 60 hours. That’s Cuba to Florida. And it’s outrageous and it’s overambitious, but I think I can make it. And that’s my last swim. — Diane Nyad, (professional marathon swimmer, age 28 years old, 1978) After a year of training, Diane Nyad attempted…