It’s hard to be a champion, and harder still to set a record. Let me look at one event in particular, the 50 meter freestyle.In this event, swimmers make one length of the pool. They simply dive in and swim. There are no turns. Well, unless they’re swimming a 50-meter short course, which uses a 25-meter pool. The cool thing about this difference is the men’s record for the long course is 20.91 seconds and the record for the short course is 20.30 seconds. Clearly swimmers get a pretty good boost pushing off the wall in a flip-turn.
Using the world record time on men’s long course, set by Cesar Cielo of Brazil in 2009, I can get an average speed for the race:
Perhaps you prefer different units. If so, this is about 5.3 mph. Of course, this includes the higher starting speed that comes with diving off the block. So it wouldn’t be unreasonable to say an Olympic freestyle 50-meter swimmer could have a speed of 2.2 m/s in the water.