2 year old son in a cast!!!

My son fractured his middle finger and they put a full arm cast on him so it covers up to his shoulder pretty much and only his thumb and pointer finger are out. It is so frustrating because you can't get the cast wet and he is a water baby!! he just wants to go swimming so bad. he got the cast put on Aug 1 his birthday was the 5th he turned two and he doesn't get to take it off until the 25!!! I feel so bad for him he hates how it is so itchy and he can't scratch it and he can't turn over in his sleep anymore it's too heavy for him to lift while he's sleeping! He normally takes a long shower and plays in his pool daily but now I'm so scared of getting it wet it's just a quick shower and definitely no pool and he's miserable. what can I do any advice momma's? did anyone else have a little one in a cast?