How cities are turning their polluted rivers into swimming havens

For most of Pauline Janbon’s life, the idea of bathing in the Seine River in Paris was unimaginable.

“As kids, we were told there were corpses floating in the water,” said Janbon, a 20-year-old student at Paris’s Sorbonne University. “It had a reputation of being extremely dirty.”

This June, however, as a record-breaking heatwave hit the country, Janbon along with thousands of other Parisians, dove into the city’s once-feared waterways to cool off. The day I met her, she was standing along the banks of the Canal Saint-Martin, surrounded by hordes of bathers jumping, swimming, and floating in the water below.

“Until today, I’d never bathed in my own city before,” Janbon said as she wrung river water out of her hair. “It feels like I’m on holiday.”

Paris is just one of many cities in Europe that has fought to make their waterways swimmable again. Copenhagen, Basel, Zurich, Bern, and Oslo have all spent years improving their sewage management systems, creating stormwater infrastructure, and implementing policies to better control water pollution. Their efforts have been largely successful, with city-dwellers across the continent returning to their waters in throes. And as climate change creates more intense and frequent heat waves, city planners and residents are also turning to these waterways to cope with hotter days.

“In these cities, we are seeing people renegotiate their social contracts with water,” said Matthew Sykes, the co-founder and program director for Swimmable Cities, an alliance of organizations championing the right to use urban waterways. “People are starting to understand that a swimmable city is a better one.”

A historic return to the waters

Until the early 20th century, bathing in urban rivers was a common activity in western Europe and parts of North America. Bathhouses were built directly on rivers and were places where people went for leisure as well as to get clean. Lack of private plumbing in people’s homes meant that these river bathhouses—popular in cities like New York, London, Boston, Philadelphia, and Paris—were often the only place where people could wash themselves.

As industrialization expanded and populations sky-rocketed in cities, urban rivers across Europe became unthinkably dirty. In Paris, wastewater, animal parts, and laundry suds were discharged directly into the Seine. As a result, the city banned swimming in 1923, deeming the water unsafe for human health.

City officials began discussing river cleanup in 1988, but it wasn’t until 2016 that Paris Mayor Anne Hidalgo renewed the city’s commitment to cleaning the Seine, making it a central pillar in her bid for Paris to host the 2024 Summer Olympic Games.

“Paris has done a lot of the heavy lifting for other cities,” said Sykes, noting that the mayor’s office was subject to a lot of criticism from media and constituents. “They had to prove that an initiative like this, which had already been tested in smaller cities, was possible in a big urban metropolis."

In July 2025, when the Seine officially opened to the public, over 100,000 people swam in the three bathing designated sites, resulting in the city extending the opening into early September. As the river enters its second swimming season this summer, Paris is proving that cleaning rivers is not only possible—but vital in the age of climate change.

In June, Paris experienced its most extreme heat wave in history. France has little air conditioning, with only a quarter of homes and fewer than seven percent of schools equipped with cooling systems. In Paris, the Haussamanian buildings that give the city its signature look are notoriously poorly insulated against the heat, leaving Parisians with few options for cooling down. As temperatures soared in late June, sweaty Parisians could be found seeking refuge in the refrigerated aisles of grocery stores and waiting in long lines to access the city’s municipal pools. But the most popular cooling option for many was Paris’ newly cleaned rivers and canals, where hordes of people descended to take their first city dip.

Scientifically speaking, Parisians have little reason to be concerned about the cleanliness of their water. Every day, the city monitors the Seine for E. Coli and enterococci, which can cause fever, urinary tract infections, and diarrhea. They have consistently found that the water is safe for swimming, according to regulations set by the European Union.

Still, for many Parisians, a mental block prevents them from swimming in the Seine. When the polling agency IFOP asked one thousand French people in 2021 what they thought of the Seine, 70 percent of respondents described it as dirty, polluted, and smelly. Few said they would take a dip. And while that perspective has started to change, the Seine’s longstanding reputation as a dirty river is hard to shake.

“I’m glad my sons can enjoy the water but there is no way I’m getting in,” said Soizic Prado, 52, as she sat fully clothed watching her children swim from a nearby bench. “I’m sure it’s safe but I’ve spent my whole life hearing that the water is dirty,” she explained. “Ça donne pas envie.”

The Swiss model

On a late Saturday afternoon in Basel, Switzerland, I packed my cell phone, wallet, and camera into a dry bag and jumped into the Rhine River, joining hundreds of locals as they floated downstream through the city center.

Though Basel is a mere 250 miles away from Paris, people's relationship with their rivers here couldn’t be more different.

“I never worry about the water quality,” Sophie Mauckenthaler, a 23-year-old student told me as she floated past the city’s cathedral. “Nobody does.”

Switzerland has some of the cleanest urban rivers in the world. The country is the international leader in wastewater treatment, every year spending on average roughly $230 per person on upkeep, significantly outpacing other European nations.

As a result, Basel has become one of Europe’s most swimmable cities. On any summer day, there are people jumping in and drinking from the city’s water fountains situated on plazas and street corners. But the most popular activity by far is swimming in the Rhine, with some locals even commuting to work by floating downstream. “We cannot understand the concept that you would have a river in your city and not swim in it,” said Ruedi Bösiger, a Swiss freshwater expert with the World Wildlife Fund. “It’s part of our culture.”

People in Basel have been bathing in the Rhines since at least the 15th century, when nuns from the city’s abbey would cool off in the river. The first official bathhouse on the Rhine is said to have opened in 1831, though archival documents suggest they may have existed before. For the past four decades, floating down the Rhine with floating dry bags, known locally as Wickelfisch, has been a staple of city life in the summertime. 

The Swiss’ relationship to their rivers, however, hasn’t been without obstacles. In 1986, a fire at a Sandoz agrochemical storehouse released toxic substances into the Rhine, turning the river red. The chemical spill decimated the wildlife living downstream and was considered one of the worst environmental disasters in the river’s history.

Even prior to the chemical spill, Swiss urban rivers were highly polluted. Like in many European countries in the mid 20th century, Swiss cities dumped industrial waste, sewage, and factory run-off into their rivers, making them unsafe for swimming.

The chemical spill in Basel, however, led to massive legislative changes throughout the country. Infrastructure was put in place to ensure spill water from a fire wouldn’t reach the river; treatment plants were updated for both industrial and household wastewater; and a comprehensive water monitoring system was implemented across the river.

“This crisis brought people together and made them aware that they had to take care of the Rhine,” said Patricia Holm, a researcher of aquatic ecosystems at the University of Basel. “As a result, the river is healthier now than it was before the spill.”

Though Switzerland is often highlighted as a success story, experts believe there is still work to do. “Just because rivers are swimmable for bathing does not mean they are intact in an ecological sense,” said Bösiger.

Water quality, which is primarily measured through the river’s E. Coli levels, does not consider the overall ecological health of the body of water. Though Swiss rivers might no longer make people sick, they have been channelized and fragmented by hydropower stations, which has led to habitat loss and limited the flow of sediment downstream, affecting wildlife and aquatic ecosystems.

Experts also say that water quality measurements need to look for micro-pollutants, such as drug residue, pesticides and parabens, which can have negative impacts on human and animal health.

In 2016, Switzerland became the first nation in the world to pass legislation requiring chemicals to be removed from water. Every year, Swiss cities are adding micropollutant treatment facilities to their existing water treatment plants.  Experts credit Switzerland’s direct democracy system with allowing residents to directly enact water regulations by proposing referendums.

For Yixin Cao, a former researcher at the Urban Bathing Studio at the University of Lyon, this unique political system has helped enable water clean-up efforts and allowed Swiss people to participate in restoring their rivers.

“In Switzerland, people understand the river as a common space and they trust it, which is a perspective that is currently missing in Parisian culture and other industrialized cities in Europe,” she said. “The Swiss have a deep relationship with their rivers.”

When I got out of the Rhine a few miles downstream in the early evening, I met Danny Wehrmueller, 66, a local theater director who had spent the day floating in the water with his wife. He said urban river swimming was “quintessentially Swiss,” but added a caveat. “When I was growing up, the river wasn’t clean enough to do this,” he said, noting for the first thirty years of his life, no one dared get in the water. “Now, we never think twice about the pollution.”

For Wehrmueller, the Rhine batheability swimmability shouldn’t be seen as exceptional. “It shows that cleaning a river, anywhere, is possible.”