The Leica X-U (photo by Leica Camera AG)
The best camera is the one that's with you, unless you've ever owned an underwater compact camera. The Leica X-U is about to change all that. Nothing on the market has ever inspired much confidence in terms of image quality, even if the waterproofing and shock resistance were neat (often essential) features. Not since the Nikonos (film) series has anything compact been worthwhile for serious underwater photos. Not counting the pro standard of using a DSLR in an underwater housing, this is the best possible underwater / outdoor adventure camera.
Even if you do count housed DSLRs as an option (typically double the cost of your camera by itself), consider that this new Leica X-U has an APS-C sensor, the same as in most DSLRs on the market today. So, what are you giving up, really? Interchangeable lenses (I would have probably put a 35mm lens on mine anyway). An optical viewfinder (difficult to use underwater) and you'll still have Live View so that's roughly the same. AND, this has macro mode plus a built-in macro flash, so no dorky, bulky flash arms protruding from either side of your heavy, borderline unmanageable underwater housing rig. In short, this camera packs a lot in a small form factor.
A visit to either the Florida Keys or maybe even the Bahamas seems necessary now...