They say that women should either wear a tampax or make sure they dont do nude hot tubs, I was always told this at the health spa's and my gym always made me aware of it, they used to say read the rules, which they know people dont.
My friend used to sell Tanning stuff & hot tubs etc, and she always advised women to not do it nude and if poss use a Tampax etc.
In my first preg I had a bath spa thingy in my bath but angled it at my back, which was lurvy.