A proper housing, makes a huge difference compared to the point and shoot.
You want to be able to set the Shutterspeed and aperture, and the ability to switch to manual focus. You need a camera that focuses and shoots fast.

You can still get great shots with a point and shoot, but you will get 1 out of 1000 if you are lucky. And very much doubt you would get a shot suitable for a mag to publish.

With a decent camera (5d,7d,600d) in a proper housing (essex,spl,aquatech) you will get plenty of great shots.

I would also recommend a prime lense or a fisheye.
fisheye is good for underwater shots, and in the barrel .
50mm would be good for kites,windsurfing,surfing etc.
I use a 50mm lens the most. the 50mm 1.4 is a good choice.
Dont bother with 50mm 1.8 as autofocus is way to slow.

Some of my shots here
500px.com:443/bigmark
I'm still learning...

Thanks for the input guys....really helps- I'm going to save up and get something good.

BTW- Bigmark, those photos are fantastic- crisp and in the action, exactly what I am aiming for and very inspiring.