Over the last century, the very suggestion of taking a dip in Paris' most emblematic waterway would have been dismissed as foolhardy at best.

But thanks to Paris Mayor Anne Hidalgo, Parisians and visitors won't have to hold their breath for much longer to swim in the River Seine without fear of arrest or bacterial infection.

Keen on combatting pollution and opening the city up to new, unexpected (and in this case, previously outlawed) recreational activities, Hidalgo has overseen the opening of a temporary "clean swimming zone" at Bassin de la Villette, an artificial lake linking Canal Saint-Martin and Canal de l'Ourcq in Paris' 19th arrondissement. Opening the basin for sanctioned swimming was a no-brainer. It's already a popular spot for clandestine backstroking and doggy-paddling. (Unlike with the Seine, police are more lax in enforcing no-swimming laws in canals.)

If the canal swimming plan goes, well, swimmingly, Hidalgo's office will turn its attention to the Seine next.

"We have reached one of our goals by opening the Bassin de la Villette to swimmers," the mayor's office explains in a news statement, adding that "while the quality of the Seine has improved recently, it has not yet reached the sufficient level for swimming."

Despite being a legendary site for romantic strolls, picnicking and, in more recent years, beach volleyball along its banks, the Seine has been off-limits to recreational swimmers since 1923. Dangerous currents, heavy boat traffic and gnarly bacteria are among the factors that have made the act of enjoying a refreshing dip in the river the very definition of une mauvaise idée — a terrible idea.

Paris-Plages, Seine, Paris Pop-up artificial beaches have been a summertime staple in Paris since 2002. Is open swimming in the long off-limits Seine next? (Photo: Bertrand Guay/AFP/Getty Images)

As for the new — and reportedly very popular — swimming zone at La Villette, it serves as the latest and splashiest feature of Paris-Plages. Launched in 2002, the mayor office's long-running "Seine-side holiday" initiative in which pop-up beaches — truckloads of sand, floating swimming pools, the works — are installed along the Seine and at La Villette Basin is one of Paris' most beloved summertime traditions. As part of Paris-Plages, congested roadways flanking the Seine have also been closed to traffic and transformed into lively pedestrian promenades, some of them permanently.

Allowing beachgoers to actually enter the water is an obvious next step for Paris-Plages. Floating sanitary (read: chemically treated) swimming pools such as the lovely Piscine Josephine Baker have proven wildly popular with the public. But there's nothing quite like cooling off in a large natural body of water, particularly one that's been off-limits for so long.

"It's symbolic," Gilles, a film director who recently took full advantage of the lifeguard-staffed filtered swimming area at La Villette Basin, tells the Guardian. "It shows a future is possible where we can reverse pollution, where we can make things cleaner and reclaim nature."

"I hate the smell of bleach and chlorine in public pools. This open-air water is cloudy and you can't see the bottom, but it makes me feel secure," he explains. "I feel like I'm taking possession of nature again."

Swimming in Canal de l'Ourq, Paris Parisians cool off in Canal de l'Ourq following a sanctioned swimming event in August 2016. This summer, bathers can enjoy a designated swimming area in the canal as part of Paris-Plages. (Photo: Matthieu Alexandre/AFP/Getty Images)

Olympics-sized push

Hidalgo's plan is that the triathlon and 10-km open-water marathon events in the 2024 Olympic Games will take place on the river, much like they did at the 1900 Summer Olympics in Paris. Following the Olympics, the river would ideally be open to all swimmers.

"This opens that door to open-water swimming in Paris," Hidalgo proclaimed at the grand opening of the designated swimming section at La Villette. "Thanks to the Olympic Games, we'll be able to see to it that the water in the Seine is clean water."

Swimming in the River Seine at the 1900 Summer Olympics in ParisThe cleanliness of the Seine has long been in question. But as the Guardian reports, city environmental authorities are increasingly confident that sections of the bustling and previously sewage-filled river will soon be — or already are — swimmable thanks to contemporary anti-pollution regulations and widespread clean-up efforts. (Worth noting: In 1870, when swimming in the Seine was a popular pastime, the river was 400 times more polluted than it is today.)

In 1988, former Mayor Jacques Chirac vowed that the Seine would be open for recreational swimming by 1994. (Better 30 years late than never.)

Jean-François Martins, Paris' deputy mayor in charge of sports and recreation, tells the Guardian that in addition to the allure of opening the once-filthy Seine for the 2024 Olympics, there's also a new sense of urgency in providing ordinary Parisians with a clean and safe place to cool off in an era when the city is experiencing more extreme summer heat.

Sunbather, River Seine, Paris Look but don't dive: A swimsuit-clad man sunbathes along the Seine in 2012. (Photo: Martin Bureau/AFP/Getty Images)

New York and London next?

Outside of the mayor's office, supporters of open swimming in the Seine and Parisian canals believe that by allowing folks to take the plunge into urban waters without fear of legal repercussion (or fear of being struck by a passing boat), they'll be more likely to become good, mindful stewards of Paris' waterways. If they're allowed to swim in the river, they'll want to take good care of it.

That said, only small sections of the Seine will be sectioned off for open swimming initially.

"Not all of it would be swimmable because of strong currents in some areas, and also because the Seine has other uses, namely the river transport of goods and passengers. So we would look to find certain places where the current is weak," explains Martins.

So far, lesser-trafficked stretches of the river near Trocadéro and the François-Mitterrand library have been identified as potential swimming spots.

Paris is far from the first major city to launch a scheme that lures bathers into once-polluted waterways.

Startups in both New York City and London, for example, have pitched ambitious swimming projects for the East River and the Thames. With the debut of the swimming area at La Villette Basin and, down the line, a swimmable Seine, Paris is diving in headfirst. In comparison, New York's +Pool (a cruciform "giant strainer dropped into river") and London's Thames Baths (a project staunch in the belief that it is "every Londoner's right to liberate themselves from the intensity of the city by swimming in the Thames") have been left standing on the water's edge. Here's hoping they're able to take the plunge soon.

Inset photo of swimming at 1900 Summer Olympics: Wikimedia Commons

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.