If a people happen to be fall into the ocean from 50m high, then would the diving pose in the olympiad make less percussion then the leg going first into the water so that the body receive less damage?.
I suspect no-one has answered this because no-one has ever attempted to model this precisely. I don't have a precise answer, but if you're prepared to accept a general one I note that very high divers all enter the water feet first not head first. See for example http://www.youtube.com/watch?v=4uHkyMh9FW4. Thus experiment suggests the body encounters less damage when entering the water feet first.
Some Googling suggests that danger when entering the water at high speed is neck injuries. The top of the head is quite blunt and the force on it is high even when using the arms to break the water first.