I hope that I don't get laughed out of the thread. I'm new to underwater photography and far from anything other than amateur status in that regard.
Some time ago my wife and I decided that we wanted a camera that we could take skiing, snorkeling, etc. One that we didn't have to worry about if it got wet, but also one that wouldn't require a significant financial expenditure to acquire. We decided on the Canon Elph Sport.
This camera uses APS film and, according to the specifications, is rated to a depth of 5 meters (16.4 feet). Now you may be laughing at this point, but I have taken this "toy" to 45+ feet while diving and it has functioned well. True the flash isn't quite strong enough to bring out natural color at that depth but it is sufficient to capture a memory or two.
I've used this camera to excellent purpose while snorkeling or diving at shallower depths. Here are a couple of photos...
This photo of a green sea turtle was taken at a depth of about 25 feet while snorkeling off of Kaanapali Beach, Maui - July 2001.
And this photo of a large green morey and shrimp was taken at a depth of 35+ feet while snorkeling at Molokini Crater, Maui - July, 2001. I was determined to get this shot, the depth made it very difficult given that I was free diving. I can only estimate the depth based on body length and some experience.
I'm finishing another role of film at the moment, it will have photos from recent dives off of Laguna Beach, in CA, and an upcoming trip to the Coronado Islands. I'll scan what comes out and post it.
This camera will certainly do much better than the manufacturer's rating of 16.4 feet, and the image quality is good enough for my humble photo album.