For the first time in over a century, Parisians and tourists will be able to take a refreshing dip in the River Seine. The long-polluted waterway is finally opening up as a summertime swim spot following a 1.4 billion euro ($1.5 billion) cleanup project that made it suitable for Olympic competitions last year.

Three new swimming sites on the Paris riverbank will open on Saturday — one close to Paris’ Notre Dame Cathedral, another near the Eiffel Tower and a third in eastern Paris.

Swimming in the Seine has been illegal since 1923, with a few exceptions, due to pollution and risks posed by river navigation. Taking a dip outside bathing areas is still banned for safety reasons.

The Seine was one of the stars of the Paris Olympics in 2024, whether as the scene of the ambitious opening ceremony or the triathlon and marathon swimming competitions. That didn't go without challenging hurdles such as rainfall increasing levels of bacteria, which postponed some competitions.

This city's authorities have given the green light for the public opening, with water quality results consistently in line with European regulations.

Making splashes in Paris city center “It’s a symbolic moment when we get our river back,” said sports coach and influencer Lucile Woodward, who will participate in the first amateur open water competition in the Seine on Sunday.

Woodward, who enjoyed a dip alongside Paris Mayor Anne Hidalgo just before the start of the Olympic Games, is confident things will go well.

“We're going to enjoy swimming in it, being there and setting an example," she said. "Once people will see that in the end there are hundreds of people who have fun and enjoy it, everyone will want to go!”

“For families, going to take a dip with the kids, making little splashes in Paris, it’s extraordinary,” Woodward added.

Olympic athletes competing in the river was a spectacular reward for the cost of the cleanup effort.

In the run-up to the Games, authorities opened new disinfection units and created a huge storage basin meant to prevent as much bacteria-laden wastewater as possible from spilling directly into the Seine when it rains.

Houseboats that previously emptied their sewage directly into the river were required to hook up to municipal sewer systems. Some homes upstream from Paris also saw their wastewater connected to treatment plants instead of the rainwater system flowing directly into the river.

Green flag for swimming Paris Deputy Mayor Pierre Rabadan said water is tested daily to confirm it's safe to swim. As on French beaches, different colored flags will inform visitors whether or not they can go in.

“Green means the water quality is good. Red means that it's not good or that there's too much current,” he said.

Tests have been in line with European regulations since the beginning of June, with only two exceptions due to rain and boat-related pollution, Rabadan said.

“I can’t make a bet on the numbers of days when we’ll have to close this summer, but water quality seems better than last year,” he added. “We’re in a natural environment ... so weather condition variations necessarily have an impact."

Last year, several athletes became ill after competing in the triathlon and open water races during the Olympics, though in most cases it was not clear if the river was to blame for their sickness.

World Aquatics stressed the conditions met the sport’s accepted thresholds.

“The legacy of these efforts is already evident, with the Seine now open for public swimming — a positive example of how sports can drive long-term community benefits,” the organization said in a statement to The Associated Press.

Skepticism remains about water quality Dan Angelescu, founder and CEO of Fluidion, a Paris and Los Angeles-based water monitoring tech company, has routinely and independently tested bacterial levels in the Seine for several years. Despite being in line with current regulations, the official water testing methodology has limitations and undercounts the bacteria, he said.

“What we see is that the water quality in the Seine is highly variable,” Angelescu said. “There are only a few days in a swimming season where I would say water quality is acceptable for swimming.”

“All we can say is that we can raise a hand and say look: the science today does not support the current assessment of water safety used in the rivers around Paris, and we think that there is major risk that is not being captured at all,” he said.

Some Parisians also have shown skepticism toward the idea of swimming in the Seine. The feeling is often reinforced by the water's murky color, floating litter and multiple tourist boats in some places.

Enys Mahdjoub, a real estate agent, said he would not be afraid of swimming, but rather "a bit disgusted. It’s more the worry of getting dirty than anything else at the moment.”

A dream come true Until the end of August, swimming sites will be open for free at scheduled times to anyone with a minimum age of 10 or 14 years, depending on the location. Lifeguards will keep a watchful eye on those first dips.

“It’s an opportunity, a dream come true," said Clea Montanari, a project manager in Paris. "It’d be a dream if the Seine becomes drinkable, that would be the ultimate goal, right? But already swimming in it is really good.”