Nikon has introduced what is being touted as the first digital Nikonos. I don't have one but just downloaded and read the manual so can make some comments re: using it for cave photography.
While there are about a dozen waterproof digitals on the market, none has ever offered any degree of manual control. This one has full manual plus aperture or shutter priority. So that's exciting for anyone who wants to do more than point and shoot photography. This thing also has interchangeable lenses and a larger sensor than any of the current offerings. The lens of most interest for cavers is their 27mm equivalent fixed They have a 30-74mm zoom that is also waterproof. Note that it takes "1" series lenses so more options but only the two that are waterproof.
At $800 it is pricey but not horrible for a product that offers many new features. After studying the manual I see some other shortcomings. There seems to be no option for direct use of an external flash. So you can't use this with radio slaves. It does have a built-in flash, but as far as I can see, you can't reduce its power in the menu. So you could run optical slaves but have to use on-camera, full power flash. Drawbacks include introducing flat lighting on closer shots and the dreaded red-eye, and the classic fogging problem of on-camera flash. Whether there are pre-flash issues too i can't tell but one probably wants digital slaves or flash that can be set to go off on 1,2,3, or even the fourth flash detected.
It allows for exposesures up to 30 seconds so can be used with LEDs or flahbulbs.
If it only had a hotshoe I would be sending my order in now. I may yet do so. Anyone wanting to do uw video in HD may want to take a look, though its only rated to 15m.
Here's a link with a bit of info:http://www.dpreview.com/previews/nikon-1-aw1/
Be interested to hear from anyonewho gets one.