I haven't personally come across or used any products to remove hair that involve soaking in the tub. I'm aware of some water resistant ones that you can use in the shower and won't wash away but haven't used them. So I can't personally comment on their effectiveness.
However, in my opinion one of the best hair removal strategies is waxing or using an epilator. which is essentially a mechanical way to to the same thing as waxing. that is removing hair from the root. it lasts from 2 to 6 week, an average of about 3 weeks. repeated waxing can damage the hair follicle so it doesn't grow back and hair tends to become finer.
the problem with creams and shaving is irritating or damaging the skin. Shaving doesn't last very long so has to be done frequently.
