I've always been happy with the walmart disposable camera. It's not the top of the line but it works!
On a clear day, I usually dive between 10 to 15 ft deep for photographs of fish and coral.Not sure I would trust a Walmart camera at those depths, but Fuji and Snap Sights have a nice underwater disposable camera for around $20. You really need a clear, sunny day to take decent photographs underwater with disposable cameras, and the depths need to be shallow as well, unless you have a strobe attached to your camera.
I attached a picture of the disposable camera I used in Dry Tortugas....purchased from a Dive shop in Fort Lauderdale.
We are looking forward to moving up to the digital underwater photography world...the images are very intense and crystal clear.