David Wilson
Contributor
May seem a little like "overkill", considering that it's your hand that needs to be kept dry, but this British drysuit company retails "dryarms", waterproof cast covers which "are good not just for casts, but any type of wound you might have to protect from getting wet if you still want to swim."
Hammond Drysuits - waterproof cast covers - dry arms - dry legs
Hammond Drysuits - waterproof cast covers - dry arms - dry legs