We’re all familiar with the range of swimwear we’d see on a trip to the pool or the beach—anything from boardshorts for teenage guys to one-piece Speedos for serious female swimmers. But swimwear wasn’t always so varied as it is today, or so revealing. Here are some interesting facts about fashion trends in swim attire in the 20th century and earlier.

Mid-1800s: Women wear “swimming gowns” made of wool or flannel (fabrics that don’t become see-through when wet). Weights are sewn into the hems so the dress won’t rise in the water. Men’s suits are also wool, with long sleeves and full-length legs.

Turn of the 20th century: Early swim trunks for men are introduced. More modern in appearance, this attire is still cumbersome: when wet, the trunks weigh as much as nine pounds.

1907: Swimmer and water-ballet performer Annette Kellerman is arrested on a Boston beach for indecent exposure. Her form-fitting, one-piece swimsuit revealed her arms and legs, scandalizing other bathers.

1920s: Although still made mostly of wool, swimwear for men and women now features colorful patterns, leaving behind the drab shades of gray and black that had been the only acceptable colors for swimwear.

1930s: Swimsuits made of cotton are finally becoming widely worn. In the early 1930s, a chest-revealing swimsuit, called the “Topper,” is introduced for men. The detachable top could be zipped away from the trunks. Still a daring concept even for men, the topless suit elicits disapproving stares at the beach—and sometimes arrest for indecent exposure.

1947: The first “bikini” is introduced after World War II. Modest compared to current versions, the early bikini is essentially shorts and a crop top that exposes a small section of midriff. The suits were named for Bikini Atoll, islands in the Pacific Ocean and the site of nuclear weapons testing. It is theorized that the swimsuit creators believed the bikini swimsuit would produce an explosive cultural shock that was equivalent to that of the atomic bomb.