Women immersing with clothing in a Mikveh, sea, or ocean:
- May a woman immerse with clothing into a Mikveh. For example, if the only place for a woman to immerse is by a sea/ocean, may she immerse while wearing her bathing suit and the like, or must she remove all her clothing which would make her feel very embarrassed and self-conscious, as perhaps someone is looking.
A woman who is a Niddah who immerses in a Mikveh with her clothing is permitted to her husband. However, this only applies to loose clothing and not to clothing that is tightly fit onto the body, as is accustomed today to be worn by woman. [Thus, if a woman immersed while wearing a garment that is tightly attached to anywhere on the body, the immersion is invalid, and she must re-immerse with a blessing. Accordingly, a woman may not immerse while wearing a bathing suit or bikini, or other under garments, and if she did so her immersion is invalid.] Furthermore, this only applies Bedieved [or in a time of great need], however Lechatchila one may not immerse with anything on the body [including loose clothing], even if it does not invalidate the immersion. [In a time of great need, such as if a woman needs to immerse in the ocean and fears being seen by the public, then she may even initially immerse with a loose garment, such as a loose nightgown, without wearing a bathing suit or undergarments.]
It is initially forbidden for a woman to immerse in a Mikveh, sea, or ocean, while wearing any clothing. However, in a time of great need, such as if a woman is forced to immerse in the sea or ocean and fears being seen by others, then she may immerse while wearing a loosely fit robe/nightgown, without any underclothing.
 Michaber Y.D. 198:46; Rambam Mikvaos 1:7; Rosh Mikvaos 28; Rav Beitza 18a “A woman may connivingly immerse with her clothing”
The reason: As the water becomes absorbed through the clothing. [Rambam and Rosh ibid]
 Shach 198:56; Raavan Niddah 327 p. 138a; Sefer Hachinuch Mitzvah 175; Beri Heiytiv of Maharit 198:31
 Aruch Hashulchan 198:91
 Minchas Yitzchak 4:35; Avnei Shoham
Other opinions: Some Poskim rule that if she immersed while wearing a bathing suit then the immersion is valid, as the water penetrates, and it does not consist of a Chatzitza. [Igros Moshe E.H. 4:14; 4:23-3; O.C. 1:54; Y.D. 4:17; Implication of Rebbe in Igros Kodesh 18:482 in a Limud Zechus of Ben Nidda]
 Makor Chaim 198:156
 Rama 198:1 in general law; Makor Chaim 198:156 that the same applies to clothing and that so is implied from wording of Michaber ibid that only Bedieved, or in a time of great need, is it allowed
Other opinions: Some Poskim rule that only if the loose clothing cover majority of her body may she not immerse with it Lechatchila, while if it only covers minority of her body, then she may even Lechatchila immerse with it. [Pardes Rimonim 61:5; 198 Miksheh Zahav 7 p. 29]
 Makor Chaim ibid