Swimming is among the most competitive sports in the world today.

Whether competing at the World Championships or the Olympic

Games, swimmers are continually improving the best times for

various events. New records are often set at these international

competitions, with just fractions of a second making the difference

in transferring the title from one phenomenal athlete to another. But

some records have remained in place for years or decades. Some

records seem nearly impossible to break. Part of the Unbreakable

Sports Records? series, Swimming Records That Will Be Tough to

Beat tells the stories of five swimming record holders whose

personal bests might just stand the test of time.