Water Polo/Diving queries

[Bede735]

I've been watching some of the swimming at the Commonwealth Games where the men wear knee length jammers and the women also wear their costumes down to the knees. At the level of course the suits are designed so that swimmers can swim a fraction faster.

So, why don't Water Polo players wear jammers, as there must be times where they have to sprint to pick up a loose ball?

In Diving, the medium of resistance is air, so it must be better to wear less. So, why don't women wear bikinis, especially as in athletics now where they more or less do?