Home > Parisians woke up to a striking change on July 5, 2025, when public swimming returned to the Seine after more than a century. After years of work and €1.4 billion ($1.5B) invested, the river now meets European water quality standards. Three official swim areas opened near landmark sites, drawing curious crowds eager to test the green-flag waters.
Daily testing with color-coded flags keeps visitors informed, and lifeguards monitor every zone. The water is described as warm and emerald-green, a far cry from its polluted past. Officials see this as a milestone following the 2024 Olympics, where weather delays revealed just how fragile the cleanup progress could be.
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Historic Ban Lifted After a Century
The Seine was banned for swimming since 1923 because of sewage and industrial dumping that turned it unsafe. Generations grew up seeing the river as something to admire from a distance. Lifting the ban this summer signals a tangible shift, with Parisians stepping into history as well as water.
Explore Paris / Instagram / Because of industrial dumping and sewage, the Seine was banned for public swimming since 1923.
However, the 2024 Paris Olympics gave urgency and funding to a plan that had stalled for decades. Organizers needed a clean river for triathlon and marathon swimming events. That pressure drove the €1.4 billion cleanup program, which included modern engineering and daily monitoring that have now transformed the Seine.
At the heart of the upgrade are new treatment units and a giant underground basin that traps wastewater during storms. This prevents raw sewage from spilling into the Seine when heavy rain hits. Those measures, unseen from the banks, are key to maintaining the water quality at levels safe for swimmers.
Hundreds of houseboats and upstream homes once emptied waste straight into the Seine. A multi-year project rerouted them to city sewer lines. Officials say this step alone removed a major source of contamination, helping bacteria levels drop to a fraction of old readings by the time the swimming zones opened.
Three Urban Swim Spots Opened
The city marked out three swim zones: one near Notre Dame Cathedral, one by the Eiffel Tower, and another in eastern Paris. Each site has a floating platform, lifeguard posts, and clear entry points. Swimmers move through designated lanes, keeping traffic orderly in what feels like an open-air pool.
Every morning, water samples are taken and analyzed before the gates open. A green flag signals safe conditions, while a red flag closes access until bacteria levels return to target ranges. This simple system has been widely praised for giving clear information to both locals and visitors.
Explore Paris / Instagram / Opening weekend readings showed bacteria counts 10 to 25 times lower than the European limits. That figure surprised even some longtime skeptics.
City leaders highlighted the data in press briefings, calling it proof that their investments had turned a polluted channel into a viable swimming destination.
While most Parisians enjoy the historic swimming, not everyone is convinced. Water quality expert Dan Angelescu says current testing methods can miss dangerous spikes that occur between samples.
His warning has fueled cautious behavior among some residents, who prefer to wait and watch instead of being first in line to jump in.
During the 2024 Games, the Seine hosted triathlon and marathon events. Heavy rains pushed bacteria levels higher, forcing delays. That episode showed the public how weather-sensitive the system still is. City engineers adjusted drainage plans afterward, making improvements that supported the 2025 opening.