On September 11, 1951, Florence Chadwick became the first woman to swim the English Channel the hard way.
Sure, there's no easy way to swim across 30+ miles of open ocean, but Chadwick chose the particularly difficult route from England to France; that is, she swam against the current. She completed her journey in 16 hours, 22 minutes, becoming the first woman to swim the Channel the hard way, and setting a new world record -- for both male and female swimmers -- for the England-France journey.
Chadwick held records for all four of her English Channel crossings, as well as her crossing of the Straights of Gibraltar.
Unconvinced that Florence Chadwick is one of the coolest athletes of all time? When she completed her first Channel crossing in 1950, the first thing she said when she got out of the water was, "I feel fine. I am quite prepared to swim back."