Not counting scenes such as mud or oil wrestling, the only one I can think of is the woman in the nude chocolate syrup vat scene in "Sweet Movie". It's not total submersion, but by the end of the scene she has had enough poured on her and rolled around in it sufficiently to be completely covered. And it is in a vat. It's just that the chocolate isn't deep enough for much in the way of submersion. If you consider the bedroom to be the equivalent of a vat, you could say pretty much the same thing for Ann Margret's chocolate syrup and baked bean scene in "Tommy".
Love you, too
