Shallow water DSLR shooting hints?

[sniper]

I've just got a housing for the camera and plan on doing some shallow water photography, just below the surface, waves ect, any hints or tips, this in a totally new area for me, I'm guessing manual focus?
Thanks Wayne

[LesPalenik]

I've just got a housing for the camera and plan on doing some shallow water photography,

I have a completely different housing. The water here is getting a tad cold for wading, but on the other hand it is much clearer than in the summer.

[sniper]

It's going to be pretty cold here too, it's around 14c where I am.

[LesPalenik]

Consider yourself to be lucky! We got today in Ontario several inches of wet snow, I hanged up the snorkel, and got out the snow shovel.
In my local pond, all frogs, snakes and turtles are now gone, only a lone muskrat was still cruising in the middle of the nearby marsh.