I do a lot of diving as opposed to snorkling so can't get away with the little "waterproof" compacts.
The waterproof compacts are not suitable, but for many small digital cameras you can cases that come in around the £200 mark. I have used an Olympus one for many years down to 30M or so with no problem, pics tend to be a bit poor on colour, mainly because I do not have a decent light to go with it - with one of those the pics come out OK, the other way to sort the colour is to run them through Photoshop - even autocorrect makes a vast difference, you can tweek even more, but that would take an age with a lot of pics.