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Note that at Traditional seminaries, such as those run by the SSPX, the Rule states that men are to be modestly covered in the hallways, on the way to shower, etc. I quote: "A seminary is not a barracks". If there were no issue with men seeing other men without shirts, or even naked, why would the SSPX have this rule for its seminaries?
When I was in the convent, yes, there were many rules addressing modesty in attire.
We were to be modestly dressed at all times. Whenever we visited the bathroom to take a shower or bath, we had to wear a bathrobe with a towel or veil covering our heads to and from the bathroom to our cells. We slept wearing a full length white flannel nightgown with a veil (scarf).
Our superiors only permitted us to use the swimming pool when students, lay professors, priests, and visitors would not see us. In other words, we could not use the pool when classes were in session or when students, professors, or visitors were on the university campus. Thus, I only remember visiting that pool a few times per year (during the one to two week summer break). Oh, it was a solar minimum during that time, so the summers were very particularly cold, and the pool water was also cold. Our superiors would give us a choice: take a hike in the foothills surrounding the property, go on a picnic to a nearby private park, take a bus to visit benefactors who had large estates, or swim in the pool. Most of us did not like to swim in the cold pool.
We were not allowed to sunbathe, and we were only permitted to swim for 30 minutes, then we had to shower and leave. The sisters rotated the use of the pool. In other words, postulants could not swim with the novices, or the temporary professed, or finally professed sisters. Besides, we were a large class and the pool room had few private changing spaces. When I entered the postulancy, there were 27 of us. In the novitiate, there were 15 novices.