that depends on how much your willing to spend. If its just for kiting, and your buying a REFLEX digital camera, id recommend the CANON EOS 350D. It is more then enough and has very good telephoto lenses.
i'd recomend a Fisheye lens to have very wide pictures where you can capture the rider and the kite. this kind of picture has to be taken very near the rider (in the water would be ideal - with the rider jumping right over you, or in your front).
this is the camera i'm talking about.
http://www.digideep.com/english/digital ... 0D-/7/2017
this would be a good water protection for it... IKELITE is very reliable in water.
http://www.digideep.com/english/unterwa ... XT/17/2074
Anyway, thats just an idea. Have a look on the camera at
http://www.cnet.com check out for its reviews, you might like it.
But 2 essencial things are definitly the underwater photography equipment and a FISHEYE lens ! that should be more then enough! loads of cameras have these 2 items as acessories. you just have to look around and choose acording to your budget!