It's horrid, horrid, horrid. Ds2 was bought some for his birthday - once he saw the blue gelatinous gloop in the bath he ran away and refused to get in. Ds1 got in - but then the "dissolver" didn't dissolve. We had undissolved lumps of slime and a child covered in blue goo. Dh was wigging out about it blocking the drain and how we can't get the bath panel off without breaking it and then we may as well redecorate the whole bedroom . We ended up scooping the lumps out by hand and draining the water through a tea strainer. Then ds1 needed a shower. Then we had to run another bath for ds2 and persuade him to come out from under the bed to get in it. It turned a quick 20 minute bath into a two hour messy affair with much shouting about blocked drains.
It is the devil's invention.
Though bless my youngest boy for the son of a pedant he is "it's not b.a.f.f is it, Mummy? It's b.a.t.h."