A long time ago I did a lot of UW photography. I had a Nikon FE2, a custom housing, double ttl strobes, the works. Traveling with that stuff was like going on a safari. It was just too much. These days I travel light. It's the only way to really enjoy what is supposed to be a vacation.
A Canon D10 takes very good pics if you take the trouble to learn how to use all its capabilities. Not professional grade, but then I'm not a professional, and neither are 99% of the divers I see burdened with all kinds of gear. I'd rather really look at things instead of photographing everything I see.
The little Canon has no housing, fits in your pocket. The only limitation is depth. They say about 40 feet. I've take mine to around 50 dozens of times, and no problems at all. I know people who take them deeper. They sell for $250 on line and will take up less room than a paperback. Just a thought based on my experience.