My DH wore them on the AquaDuck a couple of years ago, and no one said anything. We have been told at other water parks, however, that one of the reasons they don't like you to wear them is that if they hit the side of the tube, the extra traction(as opposed to bare feet) can cause them to catch and bend your leg backward, possibly breaking it. Don't know if it's true or not--that's just what we were told once.