Before Speedo, in the early 1960's there were all-nylon Ocean Champion (6" sides) and Ocean Brief (4" sides) suits. They were in solid colors, even sizes 28", 30" etc. and had almost no stretch. Two layers, like a suit inside a suit. If I downsized a few inches, these were really tight, and I enjoyed the squeeze. Here's more details
https://vintagehaberdashers.com/2013...cean-swimsuit/