Are there any opinions or “loop holes” that allow women to loosen up modesty rules at a mixed beach? I was told that many “frum” women who dress like rebitzens in their community, go to the beach in bikinis claiming that it’s allowed at a beach. What is their source if there’s any?
Rav Yitzchak Berkovits discussed something very similar to this in a shiur he gave about modesty. (There's a series of shiurim on tznius which was available by CD, which is where I heard this. The CD was sold in his shul in Sanhedria Murchevet.)
He was discussing the gemara in Yuma 47a (see here) about how Kimchas would make sure that not a single hair of her head was exposed even in the privacy of her house, and how in certain Hungarian communities this was adopted as absolute guidelines (based on the Chasam Sofer's ruling mentioned here).
Rav Berkovits discussed how this was adopted as a strict ruling without any explanation or attempt to develop a sensitivity to the concept. He mentioned that as a kid (growing up in Brooklyn in the 1950's) he remembers knowing about some women going to the beach wearing regular, non-tzanua bathing suits, but making sure that every last hair on their head was covered by a shower cap.
It was clear from him that these women were completely wrong, and were acting out of sheer ignorance. Rather than understanding the concept of tznius, and how Kimchas was so careful that even her hair stayed covered, they understood it simply as a special halacha about covering one's hair- even while wearing a bathing suit.
It was clear that he was talking about going to a mixed beach, and wearing non-tzanua bathing suits; I don't know if they wore bikinis or not. And I don't know if this was done by rebbetzins or not (hard to believe that Hungarian rebbetzins would be so ignorant at that time, but I don't know.)
It's important to remember:
- This was done out of ignorance, with no valid loophole.
- It was only common in a certain community, and possibly only a few people from that community.
- It was done by women who covered their hair in the water, and thus made the mistake.
- This was done in the 1950's (and perhaps earlier); I am not aware of any group who still makes this mistake today.
R. Yitzchak Abadi has a responsum (Ohr Yitzvhak Vol. II Inyanim Shonim # 9) about this. His answer is a resounding no. The general thrust of the responsum is not to cite specific sources that it is forbidden, but more to wonder how anyone could even think it is permitted. Interestingly, he cites a responsum of R. Moshe Feinstein and strongly critiques its lenient ruling. In the last paragraph, though, he says that it is not the women's fault; rather it is the fault of the rabbis who teach them this.