K.W.
When my son had a cast on we used a big sleeve that slips on over the cast and you pump all of the air out of it so that it suctions to the cast They sell them in different sizes worked AWESOME and my son was very happy he could take a shower! He could also swim with it on Well worth it!!
Here's something similiar to what we used:
http://www.medcareproducts.com/castcovers/prodinfo.asp?nu...