Sea and sea, Aquatica, Light and Motion, Seatool, Gates. There are a bunch of VERY expensive brands of underwater cases for DSLR cameras.
Strobe lights are usually available from the same companies. Lots to choose form, but I would start by researching Sea and Sea, Ikelite or Inon
Ikelite is a great company, and they make very useful cases, but they are not anywhere near the most expensive models out there.
I would agree that a G9 is a great camera to for recreational, underwater photography. For less than a grand, you will have a decent camera with the canon housing that you can take to 130ft. Good picture quality and video capabilities. Upgrade the case to the Ikelite and/or get the wide angle and macro wet lens kits for the G9 and you should be able to get some decent shots.
I love mine. My photography skills are still being worked on, but the camera is great.
You can check out my videos and pictures here.
www.AirInHeresReef.com
If you are a serious photographer, expect to drop at least several grand on your new kit.
Pictures aint cheap.