haslarman:

Vintage: No information.

Comments from a follower : 

The guy on the right side of the picture is wearing a cap.  Maybe a swimming cap?  This might be two swimmers getting ready to hit the pool and taking the mandatory shower. 

In San Francisco, I used to belong to the YMCA. Before it became co-ed the pool rules were that you had to shower and you had to swim nude.  Bathing suits were made of fabric that clogged the filters in the pool.

When they started letting women join, they built a women’s locker room upstairs.  The pool was in the basement.

The men’s showers had a door that went directly to the pool – the men’s locker room was in the basement as well.

There was a big sign in several languages warning that you had to be wearing a bathing suit to go out the door to the pool.  

Especially newer members or those from out of town using their YMCA travel benefits would get turned around and walk out to the pool butt naked looking for the hook they’d hung their towel on.

Historic 1912 Film Archive Swedish Lakeside

Young Men Swimming in European Lake – 1912

The video (click on the blue heading above) shows historic footage of young men swimming at a lake.  Again, during this period we begin to see inconsistencies in how these young men are dressed.  Bathing suits are becoming less of a stigma evidencing a lack of masculinity and we can see several of the fellows are wearing them.  However, they are still a minority as most are nude.

Historic 1912 Film Archive Swedish Lakeside

Red Gym’s Pool University Wisconsin–Madison

This photo from the 1940s–50s shows male students swimming nude.

Prior to February 1973, the Red Gym’s pool was for men only, and nude swimming was encouraged. That month, however, a group of female students forced their way into the tank — naked, of course — in order to liberate it from gender segregation. The Daily Cardinal covered the event (under the headline “Blue Water, White Thighs”), and within a year, the pool was coed, clothing required.

More details at https://onwisconsin.uwalumni.com/bygone/the-red-gyms-pool/