Inspired by this post from Filth Wizardry, we used some large foam stickers as bath toys while we were in Utah in December. We left the backing on, and it didn’t disintegrate. The foam stickers fall off the walls as they dry (unless, of course, you take them off first!) I imagine you could also take the backing off and give the stickers a good dunk to remove the adhesive. I’m sure the non-sticky version works even better, but this was an easy way to get the kids more excited about taking a bath in a strange place!