2 years ago we bought a Stylus 850 SW made by olympus. Cost around 200 bucks. Completely waterproof right out of the box. Takes great underwater pics and video. Up until til then we took the disposable underwater cameras made by Fuji. A lot cheaper, around 8 bucks apiece but they still took great pics. If you can afford it, I recommend the olympus because it is a digital camera and also does video and we have never had a problem with it fogging up. Plus it is a small camera that fits in your pocket.
LOVED this on our last trip to CSA & have used it PLENTY of times since. Takes decent quality pics & pretty great underwater! (And I do pro photography on the side, obviously not w/ this but I have to have decent quality).
Amazon.com: Canon PowerShot D10 12.1 MP Waterproof Digital Camera with 3x Optical Image Stabilized Zoom and 2.5-Inch LCD: Camera & Photo
(Note, it was cheaper... maybe $280? When I got it in 2011. Not sure what's up w/ that.)
I also recommend this... love being able to slide it onto my forearm while swimming.
Amazon.com: Chums Waterproof Camera Float: Camera & Photo
I bought through Digital waterproof case company | Dicapac for our first trip... huge selection to fit different cameras. Work well. Wouldnt take on scuba diving due to pressure but may be possible.