Can a person "swim" at zero gravity - in a spaceship?

It is cool to see astronauts "floating" around in space in their spaceships. I am wondering if a swimmer, like Michael Phelps, can "swim" (the breaststroke) in the spaceship. Would it be great if we could line 8 swimmers in an enclosed arena (50m by 30m by 30m), at zero gravity, and let them compete like they do at the Olympics!