Olympian task Parisian swimmers to make the most of cleaned-up Seine

Beside a sign saying "No swimming", Pierre Fuzeau defiantly pulled on his swimming cap, slipped into the green water of the Ourcq canal on Paris's northern edge, and set off with a strong front crawl.

- Angelique Chrisafis

The 66-year-old company director regularly joins his open-water swimming group for well-organised illegal dips, including in the River Seine, where swimming has been banned since 1923, largely because of the health risk from unclean water and human waste.

"I've never, ever been sick after swimming," Fuzeau insisted. "There's a wonderful feeling of freedom and boosting your immune system in cold water. There's something great about being submerged in nature in an urban setting, it's rare to have such a sense of aquatic freedom in the city, and the camaraderie with other swimmers is a joy."

Cleaning up the murky Seine to make it swimmable for athletes in this summer's Paris Olympics has been one of the longest-running, most expensive and high-stakes endeavours of the Games. The €1.4bn (£1.2bn) state-backed plan has seen years of work on wastewater management, treatment plants, filtering stations and storm basins to lower the river's bacterial contamination from faecal waste.

It is a highly political undertaking that goes well beyond the Olympics. Paris's summer temperatures are soaring amid the climate crisis. After the Games, authorities are planning to set up local beaches and swimming areas in the Seine and Marne rivers that will be open from 2025. Like Copenhagen, Munich or Zurich, Paris and its surrounding area wants residents to be able to use urban open-water to cool off-something that was common practice in the 17th century, when nude bathing was the norm.