Cliff divers usually attempt to land head first in water. Most impacts are to the tops of their heads. The force is tremendous and impact intensity increases with height and speed. The diver head butts water and pushes it aside. He decelerates as he pushes water. Imagine hypothetically, what would happen if a diver inadvertently held his head back. With is head protruding like an appendage he could see where he's going. Unfortunately, the end result may be hitting water