I have a water-proof camera case for my regular digital camera. I could not say I have had a great success with it. I believe it would take some practice, but you could make this set up work. I prefer to snurkle in a clear water on a calm day. Scuba diving is just so much harder and takes a lot more practice. You also have to watch your air, time and depth... Also, the lower you get, the stronger flash you will need since it will get darker.
I'd stick with water-proof case and snorkle.