I have had two casts, the bag didn't work to much for me either. On my second cast (it went all the up my arm unlike my first cast) I figure out that if you take a bath and hang your arm out of the bathtub it is way easier. You can still put a plastic bag over it just to play safe. Oh, and there are casts that can get wet. I don't think a lot of doctors have them though. Well I hope my method helps you.