There are some men and women that have very poor body image. They would prefer to exercise with their own sex until they feel more confident about how they look.
The entire world should be all for segregated exercise sessions, especially swimming.
If people want coed exercising, then great. But there should always be options for women only and men only.
Anyone who disagrees with this is just being a jerk.
Back in the early 60’s I was aquatic director at a YMCA (head life guard). Swim suits were not allowed, lint clogged the filters. We had different nights for men and women.
So do I. Back in my college days, I spent one summer as a life guard- swimming instructor at a neighborhood pool. One evening a week, there was a "gals only" swimming lesson followed by recreational swim. Bathing suits were quite modest. The purpose was to give nuns and others with religious restrictions an opportunity to swim within their restrictions.
Guess what? If was incredibly popular and a great evening, and not just with the target groups.