Bubble bath play dough is fun and has multiple uses! You can mold it, squish it, use it as soap, or hold it under your running bath water for a super bubbly bath!  This is excellent for sensory play in the tub! 
Use a lot or use a little. Once done, sit it out to dry and use it again and again!  Add a cedar soap dish to help it dry so you can use this over and over!