You'll see it from almost everyone - go with a manual mode when shooting underwater. Whatever you get, make sure its got a manual mode so you can set the aperture, shutterspeed, or both. If its got a manual mode, my guess is it will also have a manual white balance setting. Depending on where and what you shoot, that can eliminate the need for the strobe.
I started with a Canon S50. Small size with the case, lots of resolution, and it did have manual modes - that's pretty good. These days maybe you'd have to go with an S70 or A70 I guess, or you might be able to pick up a used S50. If you're just starting out, you will probably appreciate having a camera that doesn't take up a lot of space. My S50 flooded - I'm not sure if that was a case problem due to my taking it below the rated depth in Truk, or if I screwed up and didn't set one of the o-rings properly; a user error at any rate. I now have an olympus right now, the 5060 with the Olympus housing would be pretty good from what I've seen, but I'm still considering getting a replacement S50 to use in my WP-DC300 case, just because of the size issue for certain locations and situations (I have an external strobe and an aluminum housing for my 5050, its heavy and bulky but I do like the results and the ability to attach external lenses).