The Power of Water
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 face first. Such a landing could cause black eyes, a bloody nose, concussion and and injury to his neck or spine. In a face plant landing, water cannot move out of an extended head's way, to cushion impact. The diver is moving too fast. Water can neither move nor compress, so a diver's face and neck absorbs impact.
A diving surfboard with high nose rocker has similar features to a diver with his head held up. The extended head is an appendage exposed to impact. High nose rocker bend is also an appendage. The underside of this appendage is flat in most surfboards. When a surfboard hits water on the flat underside, it generates resistance or lift. The surfboard may dive under water after losing speed,. The initial Impact on the flat nose underside stops the surfboard and pitches the rider. As the diver's flat face absorbed impact, the flat surfboard underside does the same. Water does not move, both diver and surfboard momentarily pause on the surface. They submerge after the appendage generates drag causing enough deceleration so water moves out of their path. Drag twists the diver's neck and abruptly pushes the surfboard backward. This drag is hydrodynamic resistance.
The diver can keep his head down to avoid face plants. The surfer can use a board with less nose rocker and less flatness shaped into the nose underside to reduce catapults. A round or V'eed bow will part water and minimize abrupt deceleration. The board may continue to dive, but; the surfer is not violently catapulted. He may recover out of a shallow dive or be pitched with less force.