In the 1920s, the idea of going to the beach and actually getting into the water to swim was still relatively new. Functionality in swimwear was not as important as fashion, so the prevailing theory was that wool would help keep you warm.
As swimming for recreation came into vogue in the 1920s, makers of swimwear had to adapt and make swimwear, well, for swimming. They revolutionized swimwear material with a stretchy ribbed jersey that fit more snug than regular jersey and was certainly more comfortable than thick wool.
This made it easier to swim, but it also showed off more of a woman’s curves. Necklines dropped to deep boat necks or V-necks. Arm holes grew bigger to to making real swimming easier.
Take a look at these cool photos to see what women’s swimsuits looked like in the 1920s.