Water Polo

Here are some of the pictures I took two days ago with my Nikon D600 and 18-300 mm lens. I would appreciate any C&C so that I can improve my technique and picture quality. The bright sun created a lot of harsh shadows and it was a challenge to get players in focus and not get my camera too wet at the same time. I do feel that I should get a polarizing filter to cut on water glare, which one would you suggest?  I choose F10 to F11 to increase the depth of field and allow for a better chance to get the fast moving player and the ball in focus, the bright sun allowed for reasonably fast shutter speed.

I would like to make my pictures a lot sharper and more saturated, how would I accomplish this?

Here is a link to all the rest of the pictures on Flicker:

http://www.flickr.com/photos/vpolyakov/sets/72157632857987561/