Paris opened the River Seine to public bathing on 5 July, ending a prohibition that had been in place since 1923. The move created three free, lifeguard-supervised swimming areas—Bras-Marie, Grenelle and Bercy—along central stretches of the river and will run through 31 August. The reopening crowns a €1.4 billion, multi-year clean-up that upgraded sewers, built storm-water reservoirs and connected houseboats to the mains so the waterway could host open-water events during last year’s Paris Olympics. Each of the new sites can accommodate roughly 1,000 swimmers a day, with access governed by green- and red-flag water-quality tests conducted every morning. Demand was immediate: city officials counted about 2,300 swimmers on the first day and said nearly 20,000 people had taken a dip by mid-July. Heavy rain on 6 July, however, overwhelmed upstream drainage systems, pushing bacterial levels above safety thresholds and forcing a two-day shutdown; similar weather-related closures remain possible throughout the season. Officials describe the scheme as both an Olympic legacy and a response to hotter summers, arguing that clean urban waterways can help cities adapt to climate change. Fourteen additional bathing sites are planned on the Seine and Marne outside the capital, building on momentum from the river’s historic reopening.