The water has a double role. It absorbs the tremendous heat by a phase change to steam. But more importantly, it absorbs the tremendous acoustic energy of the rocket exhaust. A little known fact of payload design is that the acoustic loading is what's going to kill your payload, not heat or g-forces. The water keeps the shocks waves produced by the exhaust from slapping back off the hard surfaces and damaging the rocket, the launch pad, or the payload. Even so, the F-1 plume consumed about 3/4 inch of the plume deflector surface.

Propulsion engineers drool over the Rocketdyne F-1 the way car enthusiasts drool over a '67 Mustang convertible. There is so much interest in its development, specifications, and operation that to claim it was just a big farce is tantamount to psychosis. The principles of rocket engine design are no mystery, and the appropriate features of the F-1 are well known and easily measured on the surviving specimens.