When a diver jumps off a diving board into a pool, while in the air, it is easier to somersault while their body is tucked into a ball-like shape and harder while their body is extended?

It is easier for a diver to attempt a somersault from a divering board in a pool when their body is tucked because they can conserve momentum. Due to the law of conservation of momentum keeping the limps tucked close, allows the diver to turn faster.