How fast are the swimmers moving when they strike the water?

Toruko

Terminal velocity of humans in free- fall over 80 feet averages 120 miles per hour. Cats tend to survive falls better upwards of four floors but no higher than the 9th floor. They can leg spread enough pelt and tissue to slow their descent after a second or two from instinctive response.

Michael

depends on how much force thy jumped with, and how far they fell.