With my rudimentary knowledge of physics, I would assume that helicopter blades and a rotor, although designed to hold the weight of the aircraft and its occupants, are not designed to slice through water. Given the level of resistance water provides, the speed with which the blades slice through the atmosphere, and the fact that a falling human hitting water at terminal velocity ends badly for the human, it's not really possible for a helicopter to push water the way a water propeller is designed to do.