I think what you have to weigh is cost versus quality of the photos. Like anything related to scuba diving, an underwater photo rig is expensive. I can (and will) recommend a setup for under $1000, but the camera itself is just a P&S - if you're expecting DSLR quality you're going to be disappointed. Are you going to be happy spending that kind of money to get photos which, while certainly very memorable for you and something you couldn't capture otherwise, are likely to be a noticeable step down in quality from your above-water shots? Maybe you don't spend the money on a photo rig and just enjoy the diving (the physical effort of positioning yourself for a shot can shorten your dive, and focusing on one photo op may lead you to miss something else worth seeing) - maybe put that $1000 budget toward chartering dive trips to even more exotic sites. Or maybe you spend the extra money (and go a bit in debt) to get a case and strobe for your main camera so that you're familiar with the controls and the quality - after all, these may be once-in-a-lifetime shots, so it's your judgment what that's worth to you. And since a scuba certification never expires you can use whatever you get long after you leave Okinawa, even if it's just shooting underwater in swimming pools or the occasional vacation to a scuba paradise.
I'm trying not to sound like I'm steering you one way or the other, I just want you to seriously consider all aspects, both short and long term. I got an underwater rig before I honeymooned in Australia and dove the Great Barrier Reef. I'm extremely happy I got the rig, the shots are great memories and some of them are halfway decent. But that was also
before I got my DSLR. Now that I've been shooting with my DSLR for a few years I would
much rather have had it on those dives, even if it meant taking a bit longer to pay it off.
All that being said (and remember, I was happy with my rig at the time), what I got was basically this setup:
SeaLife Cameras - Underwater Digital Camera - DC600 Elite Set. It includes: a simple point and shoot (small enough to actually be useful to throw in a pocket for vacation snapshots, but probably not for serious out of the water photography); a waterproof housing; a strobe; a mounting bracket; a wide angle lens (which can clip into the bracket when not in use and is very useful if not downright required underwater due to the way light behaves in water versus air); plus a padded travel/storage case and accessories such as dessicant. A quick check on scuba.com has this for ~$800.
I've seen a few scuba-related threads on here, so feel free to search, start threads, or PM me if you have any other scuba questions (photography related or not).