Four days after a nuclear bomb was first detonated over the Pacific islands of Bikini Atoll in July 1946, the French designer Louis Réard launched a provocative two-piece swimsuit at a poolside party in Paris. The two events might not seem to be connected. But Réard, who had been looking for a name for his design that would embody the tiniest garment imaginable, combined with the most explosive impact possible, hit on the almighty atomic blast as the ideal symbol. And so the modern bikini was born. The world’s first bikini now hangs on a mannequin in the Design Museum in London, looking decidedly less earth-shattering than it did back then. Formed from baggy triangles of pink fabric, printed with a newspaper pattern and tied together with string, it looks a bit like someone has fashioned a quick cossie out of a few pages of the FT. “It was really controversial at the time,” says fashion historian Amber Butchart, curator of Splash! A Century of Swimming and Style. “Swimsuits were getting smaller and smaller in a kind of arms race, tied up with the excitement of the atomic age.” Two months earlier, another French fashion designer, Jacques Heim, had unveiled his own two-piece swimsuit at his beach shop in Cannes. He christened it the Atome, after the particle of matter, and hired skywriting aircraft to advertise “the world’s smallest bathing suit” over the Mediterranean. Not to be outdone, Réard hired his own skywriters to fly over the French Riviera, announcing his bikini to be “smaller than the smallest bathing suit in the world”. It was the first time a swimming costume had plunged below the navel, to the horror of the Catholic church, and the glee of the male gaze. Réard was quick to capitalise on its minimalist credentials. Long before the arrival of the microkini, he published adverts declaring that a two-piece suit wasn’t a genuine bikini “unless it could be pulled through a wedding ring”. The competitive shrinkage of swimwear is one of many stories threaded throughout this illuminating exhibition, which charts our enduring relationship with water over the last 100 years, across fashion, architecture, sport and more. It touches on the British love of lidos, the lure of the seaside and the rise of wild swimming, as well as delving into more niche topics, from the controversies around hi-tech performance swimwear, to the curious Mermaidcore trend of the 2020s. The inexplicable popularity of the Dryrobe as an item of everyday clothing gets a look-in too. As unlikely as the towel-lined changing gown becoming an acceptable thing to wear to the shops, the atomic-bikini period is one of the stranger moments in the history of the swimwear-industrial complex. Displayed next to the first bikini, a 1950s photo shows people lounging beside a hotel pool in Las Vegas, as a mushroom cloud erupts on the horizon. Another shot depicts a poolside showgirl wearing a jaunty mushroom cloud headpiece. It turns out that the nearby Nevada Test Site made the area a hotspot for “atomic tourism”, with Vegas casinos offering atomic-themed cocktails and Miss Atomic Bomb pageants – where evermore skimpy bikinis were naturally all the rage. Keen not to be left out of the scanty swimwear craze, men soon got in on the action. One vitrine is dedicated to the furtive rise of gay men’s swimming attire, at a time when homosexuality was still illegal. Raunchy “physique” magazines of the 1950s and 60s, ostensibly marketed as male health and fitness publications, doubled up as softcore porn, featuring adverts for mail-order posing pouches and revealing trunks. “You’ll be number one,” promises an ad for a tiny pair of shorts with strategic windows cut out of the sides, published in a 1962 issue of The Young Physique, “when the gang gets a glimpse of you thru porthole cutouts.” Who could resist the “skintight muscle-conforming knit” of the latest “Orlon-Wool-Rubber” blend? Available in alligator skin vinyl, too. Such technical material innovation is probed further in the evolution of high performance Olympic swimwear, most contentiously in the form of the 2008 LZR Racer swimsuit. Developed by Speedo, in collaboration with Nasa scientists, the futuristic garment looks like something from Batman’s wardrobe. It was made from ultrasonically welded low-friction fabric to repel water, with compression panels for streamlining, as well as trapping air for increased buoyancy. The full body-length design instantly saw countless world records shattered: 94% of the gold medals at the 2008 Beijing Olympics were won by swimmers wearing the sleek suit. The international swimming federation, Fina, was furious, declaring that the level of innovation amounted to “technical doping”. It was one step of ingenious design too far, and was swiftly banned. Perhaps in future contests, athletes should all be forced to compete in the standard issue grey woollen onesie that used to be rented out to day-tripping bathers by the municipal Margate Corporation in the 1920s. In the days before most people had their own swimming costume, its unisex one-size-fits-all design ensured it could fit swimmers of all body shapes. A century later, the exhibition shows how similar design principles are being embraced today, in the re-emergence of gender-neutral swimwear, created by companies such as the Portland, Oregon-based Beefcake. Its one-piece swimsuits, “for any body, anywhere”, take inspiration from the classic costumes of the 1920s, with sizes ranging from XS to 5XL, made in small batches by people in Portland making a living wage. Beefcake’s Dreamboat design is shown alongside other efforts to make swimming more inclusive. There is Rebirth Garments’ trans-friendly kit – which includes a compression lining in the bottom half to suit a trans woman, transfemme or non-binary person – and elegant unilateral mastectomy swimwear by Eno for single-breasted people. The Blob swimsuit, meanwhile, was designed by Hannah Whelan as a piece of “artivism” to open up conversations around menstruation, period stigma and swimming, with a bright red patch emblazoned on its crotch. There are plenty more design stories to discover. Along with the actual red costume worn by Pamela Anderson in BayWatch, there’s a celebration of the reinvention of Penzance’s 1930s Jubilee seawater pool, recently upgraded with geothermal baths by Scott Whitby Studio, who were also responsible for the exhibition’s punchy design, drenched with bold, kiss-me-quick colours. Marvel, too, at the evolution of goggles – including a 1940s guide to making your own wooden Hawaiian diving variety – and ponder the unlikely high-fashion adoption of pool slides worn with socks, thanks to a 1990s Tommy Hilfiger campaign. Diver Tom Daley also features with his Made With Love knitting kits, as does the recent revival of budgie-smuggler briefs, for which he is partly responsible. We’ve come a long way since 2009, when Alton Towers banned Speedos, in an apparent attempt “to maintain the family-friendly atmosphere at the resort”. What would the theme park make of someone turning up in the 2-metre long silicone mermaid tail? One such scaly pink fin – made by special effects designer Silvo Dordevic, AKA Siki Red – hangs momentously from the ceiling, as an example of the subcultural phenomenon of Mermaiding. The TikTok trend, which sees people dressing up and swimming as merfolk – and greeting each other with a cheery “shello!” – has been fuelled by the live action remake of The Little Mermaid, and the Netflix series MerPeople, both released in 2023. Mermaid academies can now be found from Bournemouth to Boracay island in the Philippines. It might look like child’s play, but it’s not for the fainthearted. “It’s one of the most physically uncomfortable situations you can ever be in,” according to Morgana Alba, founder of mermaid group, Circus Siren Pod. “You can’t breathe. You can’t see. You can’t really hear. You’re probably cold. And the tail is dragging you down.” On a basic human level, “our bodies don’t want to be under those conditions”. So, perfect for the next extreme fitness trend! Like beach pyjamas and Dryrobes, watch out for these scaly prosthetics appearing soon on a high street near you.