Hawaii Tourist Bureau advertisement • 1923
This photo of the surfer is interesting because the tanline on his upper torso shows that he has been wearing the usual men’s one-piece tanksuit most of the time.
Men shifting from garments that covered their chests, to just trunks, was a part of the general social changes that occurred in the 1920s. This was somewhat daring at the time, and some people were offended by it. It wasn’t until the early 1930s that the permanent change had happened.
Swimwear styles can be a great help in determining the age of an undated photo.