The historical clean-up of the Seine River, a project costing 1.4 billion euros, aims to restore the once polluted waterway. For more than a century, swimming in the Sena was forbidden due to its dirty and polluted state. The legacy of the 2024 Olympic Games seeks to overturn this ban, allowing swimmers and divers to enjoy the water again.

Officials have been going after homes upstream of Paris and houseboats on the Seine that were emptying their sewage and wastewater directly into the river. An Olympic law adopted in 2018 gave moored boats two years to hook up to Paris' sewage network. Sewage treatment plants on the Seine and its tributary, the Marne, are also being improved.

After years of clean-up efforts, the river will be reopened for swimming in 2024, when it will host Olympic swimming events. The revival of swimming in the Seine is part of a global trend of improving the quality of city rivers. Other cities that have made progress in cleaning up their rivers include London, Copenhagen, and Beijing.