I don't know what a dilantant is, but in order for a human to maintain a high speed, he is pushing -- nay, driving -- his feet into the running surface. Water

I don't know what a dilantant is, but in order for a human to maintain a high speed, he is pushing -- nay, driving -- his feet into the running surface. Water does not provide this level of resistance for something with a high psi such as a human foot.