Question

A diver in a swimming pool bends his head before diving because it

Answer 1

a diver in a swimming pool bend his head before diving because because the head the head applies more magnitude of force because the area of the head then the whole body is smaller and it is easy to dive in a pool with a lesser thrust area

Answer 2

In competition swimming the swimmer needs to get as much speed and distance out of the dive as possible. The swimmer starts out by crunching down into a hunched down position. When the start is given, the swimmer will straighten their body and throw their arms forward while pushing off with their legs as hard as possible. This gives them the most forward momentum. As the swimmer enters the water they will angle their body downward to enter as smoothly as possible (a splash is wasted energy). The swimmer then straightens back up as shallow as possible to keep as much of their dive energy as they can. A good dive can help win a race.

Divers who are competing in a diving competition do twists, and summersaults in order to get judged on how well they did the dive, how easy (cleanly) they made the dive, and by the level of difficulty of the dive. You can get a very high mark on an easy dive and lose the competition to a person who didn’t do as well on a much harder dive.

So, that’s the best I can offer as the question is not clear, sorry.