Paris allowed public swimming in the River Seine on 5 July for the first time since 1923, marking a milestone in a decade-long campaign to clean up the capital’s iconic waterway. The decision, hailed by city officials as an Olympic legacy, followed last year’s successful staging of open-water events in the river during the 2024 Games. Three designated zones—Bras Marie near Île Saint-Louis, Grenelle by the Eiffel Tower and Bercy in eastern Paris—are open daily, free of charge, and can together accommodate more than 1,000 swimmers until 31 August. Twenty-seven lifeguards are on duty and a beach-style flag system indicates whether the water meets health standards, based on laboratory tests conducted every morning. The reopening crowns a €1.4 billion remediation programme that connected thousands of homes and houseboats to the city’s sewer network, upgraded treatment plants and built large rain-water retention basins to stop combined sewer overflows. Similar bathing spots are planned at 14 locations upstream and on the Marne as water quality continues to improve. The initiative remains weather-dependent. Heavy rainfall the day after the launch raised bacterial levels and forced officials to close the three sites on 6 July, underscoring the river’s sensitivity to runoff pollution. Authorities said they would resume swimming as soon as test results fall within regulatory limits, potentially later in the week.