All of the required swimming came as a bit of a shock to astronaut Mike Massimino, who's said that he barely knew how to swim when NASA selected him for astronaut candidate training [source: Massimino].
During a candidate's first month of training, he or she must pass a truly rigorous swim test. Would-be astronauts begin by swimming three full lengths of a 25-meter (82-foot) pool without stopping. Oh, and did we mention that the swimmers need to do this while wearing tennis shoes and a flight suit weighing around 250 pounds (127 kilograms) [source: Ward]?
When completing this portion of the test, astronaut candidates may use one of three strokes: the freestyle stroke, the breaststroke or the sidestroke. They're allowed to take as much time as they need but immediately after they've completed all three lengths of the pool, the candidates then must tread water for 10 minutes. NASA also requires its astronauts to become scuba certified [source: Clement]. We'll explain why later.
Astronaut candidates with no prior piloting experience are also put through a Navy-run water survival training course. Among other things, the trainees are taught how to deploy rafts and engage with rescue vehicles. For many years, astronauts went through the entire ordeal in the Gulf of Mexico, but the course was recently been moved into an indoor pool at a military station in Pensacola, Florida [source: U.S. Air Force].
As for Massimino, he passed his swimming and water survival tests with flying colors. And poetically enough, the astronaut took one of Michael Phelps' swim caps into orbit on his last space flight [source: Discovery].