There is a limit as to the depth that cameras can go without imploding. That's why the Ikelite housings are so expensive - they're good to 250'. I'd take a cheapie waterproof down about 10' but wouldn't want to go much further without taking a chance of having no pics at the end of the day.
I've got an Ikelite and must say that they're value for money - they're rugged, well built and all stainless connections, etc.