The gemorah mentions an issur for one to cover their place of milah when going to the bathhouse. This is brought down l'halacha in the Magen Avraham and the Mishna Brura in the begining of Siman 2. If so, how can it be that the Rama in Even Ho'ezer quotes the Agudah (Pesachim 51a) that in his time, it was the custom for people to cover themselves in the Bais Hamerchatz?
Dov Lew
The Shulchan Aruch (OC 2:1) describes how a person should get dressed without exposing his body unnecessarily. The Mishnah Berurah (2) quotes the Magen Avraham who wrote that in the bathhouse, where nakedness is not inappropriate (since one needs to bathe), it is permitted to be uncovered.
The Gemara distinguishes between going into the river when it is improper to cover the place of the Bris Milah and emerging from the river, where one faces other people and it is correct to act with modesty. This distinction should apply equally in a bathhouse. Where a person is facing others and covers himself modestly he would not be considered to be denying the Bris.
In Even ha'Ezer 23:6, the Rema quotes the Agudah who says that in his time the custom was to wear a covering in the bathhouse. As is evident from the case, other people were present in the bathhouse and therefore it would not be a problem to be covered. Moreover, if it was the custom to be covered, then being uncovered would be a breach of the Halachah of O.C. 2 quoted above!
The same idea would apply to swimming in a public place today where the custom is to wear bathing suits. We would not say that someone who goes into the water wearing a bathing suit is denying his Bris.
All the best
Ilan Segal