Cold ice mixed with hot water makes for fun in the tub. I just ran across this tub time activity from Rookie Moms that will have your kids begging for a bath twice a day (is that good or bad?).
Collect a few toys that can be played with in water. We used toy cars, plastic blocks, plastic rings, etc. Place the toys into zip baggies or plastic containers filled with water and freeze them until solid.
Once the toy in water is frozen, you will need to let it thaw for a moment or run the container under water. Then open up the zip bag or container and plop the frozen toy into the warm tub water. I found I like the plastic containers best and they are reusable. The zip bags kind of froze altogether and were trickier to remove.
Your child can have fun waiting for their toy to un-freeze as they play in the tub. You can count how long it takes to thaw out as is gets smaller and smaller. My kids loved this and I am sure we will now be finding all sorts of things to freeze for the next Ice Cube Tub Time.