On the options you have for U/W photo setups:
Minimum price, minimal control: disposable cameras and cheap underwater 35mm point and shoots.
Maximum quality: interchangable lens 35mm with manual exposure and manual focus control (either U/W native cameras like the Nikonos V or a housed surface SLR) (results are worlds better quality than any disposabl)
Maximum convencience and ease of use: housed digital cameras (results are worlds better quality than any disposabl)
Dipsosables suck because you will be using high speed color print film without any real exposure control using a fixed focus 1 element molded plastic lens. If it has a flash it is going to give bad backscatter because the flash will be so close to the lens. These cameras are pretty much useless except for vacationing snorkelers. Even a 35mm UW point and shoot like Sea & Sea or Motor Marine will allow you to use a slow speed color print film, black and white, or slide film (though the exposure systems are usually not good enough for good results from slide film). That at least affords you *some* sort of control.
If you really want to do UW photography, shell out $$$ (at least $500 if you are smart about it on ebay) and buy a camera camera(/housing), whether it is digital or film rig.
If you are questioning whether you want to do U/W photography, rent a camera rig. Lots of shops will rent Nikonos V. See if U/W photography really grabs you.