I cannot be too sure of what you mean by white stuffs but I
guess you know what you are saying. The water is either at a high
temperature or ice-cold, so chances are the little wormies may not survived much less the
equipment. 
In any case, you can still find these hot bath, mixed types in the
remote village in Japan. In the city, you would probably find a
seperate one for both sex.
As a foreigner, chances are you may find it near to, not entirely,
impossible to get entry. There was a joke when I was there in Osaka
in the early 80s that when they see if you have other ideas before
going in, you will be given a rubber band! Get it?
Anyway, it has got very much to do with culture but I do not know
for the children to bath with the parent, up to what age its not
encourage?
In Singapore? Yes! if you have the where(home), place(bathroom big
enough) and $$$(your utilities bill will tell). My friend with his
wife and 3 kidies does enjoys this in Perth, but I do not know at
what stage(undress or dress) as the eldest is a 5-year old
girl.
