I'll echo the recommendations for a housing on a regular camera you're familiar with. I'm currently using an Canon Elph 300 HS and the Canon housing for it. I got some pretty good shots out of it on my last trip:
Video, too.
http://www.youtube.com/watch?v=i3c4F...layer_embedded
I'd also say to get to the point where you are comfortable using it before you get in the water. Understand which buttons are where and how it works. Trying to learn/understand that while underwater and remembering the dive stuff really takes away from that side of the fun.