In 1896, swimming became an official sport of the first modern Olympics, even though the swimwear of that era seemed designed to slow swimmers down. Common woolen swimsuits, or bathing costumes, as they were called, were thick and heavy, making it difficult to maneuver in the water. At the time, both men and women were legally required to be fully covered from neck to knees when on a public beach. White or skin-colored fabrics were also forbidden because they revealed too much of the human anatomy.
In 1917, the American Association of Park Superintendents published its official “Bathing Suit Regulations," which required men’s suits to have a skirt that covered the shorts. For women of the era, stockings were still a customary part of the female bathing suit. These strict rules began changing in the 1920s, as evolving social norms allowed men and women to spend time together near the water, and show a bit more flesh, thus propelling swimming as a leisure activity. The sport’s physical requirements provided the perfect justification for slimmer bathing suits made from lighter materials.
Actor and Olympic swimmer Johnny Weissmuller’s 1929 portrayal of "Tarzan," for which he wore only a loincloth, made it more acceptable for men to swim shirtless, although it was still illegal in public places. During the '20s, men's swimsuits of jersey, silk, and rayon (advertised as “artificial silk”) first entered the marketplace, while major companies like Jantzen got their start in swimwear.
Jantzen began as a small knitwear producer in Portland, Oregon, but after a special design for rowing trunks became a hit, the brand started experimenting with swimwear. The company's first wool bathing suits for men were bulky and uncomfortable, weighing up to nine pounds when wet. However, the company soon pioneered a stitch that created a body-hugging fit that didn't sag when wet, and in 1927, Jantzen adopted the advertising slogan, “The suit that changed bathing to swimming.”
Around the same time, the Australian brand Speedo began dabbling in athletic swimwear. Company founder, Alexander MacRae, was originally in the hosiery business, providing socks for the Australian military, but he added his first line of swimsuits in 1927, which included a controversial women’s “racer-back” costume. The following year, a staff marketing contest yielded the slogan “Speed in your Speedos,” and the name stuck.
Unfortunately, the company’s revealing swimwear was still cause for alarm, and when swimmer Clare Dennis wore her shoulderless Speedo swimsuit to the 1932 Olympics, she was nearly disqualified for showing too much skin. In 1936, the Australian men’s team also caused an uproar when they competed in their bare-chested Speedo swimming shorts.
To satisfy the censors and flesh-demanding public, swimwear companies began selling the “Men's Topper” during the 1930s, a convertible swimsuit whose top could be removed with a zipper. Finally, in 1937, American men won the right to go topless in public, thanks to vigorous campaigning by the “no-shirt” movement...
Though stretchy Nylon and Lastex materials joined the swimwear arena during the 1930s, men’s trunks were often belted for a more secure fit. The introduction of Lycra, a version of elastic Spandex, in the late 1950s, made swim trunks even more flexible during the 1960s and '70s.
Around the same time, as surf culture hit its stride, boys wanted to be seen in longer surf trunks or boardshorts, originally worn to protect the skin from getting roughed up against a wax-coated surfboard. These trunks were often made of quick-drying polyester or nylon with a rigid waistband that tied in front, so a wave couldn’t whisk them away. The sporty boardshort style has since become standard among men's swimwear makers, with shorter trunks projecting a classic, vintage vibe.