A, if the water is shallow enough that the person diving might make contact with the obstructions damage to the body could certainly occur. The only difference between diving the same distance with water vs directly hitting the obstructions is that if there is enough water it can slow the momentum of a person so that it takes more time to go the same distance. The same distance over a longer period of time results in less force per second which if ovibously better for the human body.
