Ree-fready-I personally like Canon's line of digital cameras. They have been around since the wheel, have really nice lenses, easy to learn and use, great reliablity, and best of all-you can buy an optional underwater housing good for 30m(or any size reeftank
) for most models.
I use a Powershot S230 which comes with many features which I will list only a few:compact design, full metal body, rechargable lithium battery, full manual and auto settings, 3.2 mgpx, 3 min. video with audio, 3x opt and 3x dig zoom, plus many many more great features! And no, I don't work for Canon-although I wish I did.
My personal advice is to take all features into consideration, choose a brand that's been in the industry for a long time. Another thing to consider is power source, as these units tend to suck back the juice- so if you can get a camera including battery and charger you will be saving at least $50 right from the start. Media is also something to consider, 75% of all digital cameras come loaded with a small memory card or stick so you will have to buy larger memory from the start-unless you can handle only taking around 8-16 images at a time.
My final piece of advice would be to choose a model of a minimum of 3 megapixels, because you never want to to run short of pixels when you want to enlarge a print of your favorite coral or fish
Hope my 2 cents helps out
happy reefing/shooting
cheers, Rich