 During the 1920s and 1930s , people began to shift from " taking in the water " to " taking in the sun " , at bathhouses and spas , and swimsuit designs shifted from functional considerations to incorporate more decorative features . Rayon was used in the 1920s in the manufacture of tight @-@ fitting swimsuits , but its durability , especially when wet , proved problematic . Jersey and silk were also sometimes used . By the 1930s , manufacturers had lowered necklines in the back , removed sleeves , and tightened the sides . With the development of new clothing materials , particularly latex and nylon , swimsuits gradually began hugging the body through the 1930s , with shoulder straps that could be lowered for tanning . 
