It is a historic moment for Paris residents but perhaps a dubious one as well, after several swimmers got sick after competing in the open-water races at the 2024 Paris Olympics – although it is not clear if this was due to the water itself, and the World Aquatics governing body said the Seine met necessary thresholds.

A century ago it became illegal to bathe in the waters of the French capital due to severe pollution. In the late 18th and throughout the 19th century, human waste was used for fertiliser. But as alternative fertilisers became more common, sewage was increasingly fed directly into the Seine, making it unfit for bathing.

For many Parisians, their ideas of the Seine are less than romantic: with its fast-paced murky water, floating trash and the occasional 2-metre-long catfish, it's a river full of surprises.

But their presence might actually be a sign that the Seine is getting cleaner, according to Paris town hall. Due to purification efforts over the past 40 years, 34 species of fish now swim in Parisian waters – as opposed to just two when these efforts began.

As of today, one more species joins them: humans. Three official bathing spots are now open, one at Bras Marie near Île Saint-Louis in the 4th arrondissement (district), another at quai de Bercy in the 12th and one at Grenelle in the 15th.

Swimming within sight of the Eiffel Tower

At the Grenelle pool, which lies in the shadow of the Eiffel Tower, a long line of curious – and some might say, courageous – swimmers queued up, ready to test the waters.

Aglaé Janel, 33, a mother of two, said she felt confident letting her children swim in the Seine.

“We’re not going to let the children drink the water, we’ll keep an eye on them, but we trust it,” she said.

This site has a safety pool for families with children that is only 40 to 60 cm deep and has a lounging area for sunbathing. The venue can hold up to 200 people at once, including some 150 in the 60x20-metre bathing area, and is accessible to those with limited mobility.

Some, however, remain sceptical. Retired physical education teacher Isabelle Langlois, 67, came for opening day, but she expressed mixed feelings about the Seine's cleanliness.

“I trust the city of Paris for the tests and everything,” she said. “And I tell myself that even if there’s a little bit of pollution, we can still try to swim.”

But she also pointed out what she regularly sees from her bike rides along the river. “There are a lot of water bottles, a lot of things still floating in the Seine. Much less than before the Olympic Games, but still a lot of waste – maybe blown in or thrown by people.”

But some of the scepticism seemed to cool off as swimmers got in the water.

“We were super nervous about it at first. I said I wasn’t going to get in the water, but it’s actually really nice, and it feels clean. There’s some little bits of debris, but... it's been really cool, actually,” said Kathryn Boccuzzi, 43, an American expat who has lived in the Paris area for many years."We’ll probably come back and do it again."

People were jumping off the main platform, kids splashed excitedly in the shallow pool, but it seemed to be the adults – long-time Parisians dreaming of this moment – who were most moved by the experience.

The swimming pool is integrated with the river's natural environment, fed by water directly from the Seine. It is separated from the river itself by buoys marking swimming areas and accessed via floating pontoon decks.

An Industrial dip

At the Bercy site, many were surprised by the cleanliness of the water – especially given the surrounding high-rises and industrial setting.

“When I saw all the industry and thought about the pollution, I was sceptical,” said Morad Aref, 21, a Canadian student. “But when I got in the water, it was great. The temperature is perfect. I live in Ireland, and the beaches there are freezing, but here it’s so nice.”

Students lounging in one of Bercy’s two swimming zones were also impressed. American student Jacob Nelson, 26, said he felt safe thanks to the constant monitoring and water conditions posted at the entrance.

“It felt just like a lake,” he said. “I mean, there’s bits and bobs floating around, but it’s just plant matter – you’re not freaking out. And every now and then, you’ll see a fish swim by. I mean, if there are fish in the water, it can’t be that bad.”

Massive retention basins capture and store rainwater and sewage overflow during storms to prevent spills into the Seine. Swimming sites and weather conditions are monitored daily.

People from all over the world will be able to have a dip in the iconic Seine until August 31. Paris’s town hall has determined that winter swimming will not be possible due to higher precipitation and stronger river currents.

Some bathers are hoping that the start of swimming in the Seine will be a game changer, given that European summers are expected to become even hotter and dryer in the future.

“It feels like we’re living through a historic moment, one that will change Paris in the summers to come, given climate change,” said student Mathis Beautrais, 21.