This is a really weird product from UK, it's called Gelli Baff. The add says that it "turns bath water into goo... and back again". Well, that is exactly what it does. And it comes in some pretty funky colors (there is even a color changing version). But it won't stain kids, towels or carpets. Chemically speaking it is a powder similar to one used in disposable diapers (sodium polyacrylate to be exact). It can hold 400 times its own weight in water.
So, in the box you get two packets. You fill the bath tub with warm water and add the packet #1. The water turns into brightly colored goop. Not slimy goo, though, something like gelatin. Your kid -if he is an adventurous type- jumps in and hopefully has a good time. When he's done, you add a packet #2, which is pure table salt. The goo turns back into liquid, that is safe for the septic system. You rinse the child and he is good to go.
Here's a TV commercial:
But the question is, would you buy it? Do you think your child would get in?
The official website is www.gellibaff.co.uk