Thanks for the very helpful replies. I haven't looked at the disposable underwater ones, I guess the best course of action is to try them both, I only looked so far at KEH, and the only model I remember is the IV-A. My shots will be mostly on saltwater, and a few on freshwater ( I can't swim in pools, my skin gets irritated). I will look up that link in Ebay.
As for the lens, 20-28mm is what I'm after, or 35 can be also.