Vintage swimsuits in the 1940's and 1950's had far a greater variety of swimwear fabrics, like lined cotton, stretch latex and nylon. The new bathing suit of that period was tailored to flatter a womans figure with tummy control panels,support cups for the bust and boning to create an hourglass figure.
This charming film from 1948 gives us a good idea of what was popular in the early post war years