http://www.ebay.com/itm/271225349376
These vintage swim trunks were made by Jantzen in the late 1930s. This particular model was known as the “half-hitch”, after its half-concealed belt. That model was made from about 1937-1942. This is one of the earlier versions of it. Unfortunately, they are heavily moth eaten.

Waist (unstretched): 13″ (doubled = 26″)
Waist (stretched): 19″ (doubled = 38″)
Side Seam: 10-1/2″
Rise: 14″