I just purchased underwater housing for my canon 990, its a point and shoot, uses the built in flash, seems to work ok, and it will do video. The problem with all underwater cameras, (both video and still) is that to get good shots, require lots of addtional light. Depends on how serious (read $$$) you want to be.
The canon990 was around $400us and the housing was $200 us, don't forget the weight kit, and addional $25 us. Check the forums at scubatoys.com for more info