Paris — The City of Light placed the Seine river at the heart of its bid for the 2024 Summer Olympics. The opening ceremony will be held along the Seine, and several open water swimming events during the games are set to take place in the river.

Paris Mayor Anne Hidalgo had vowed that the Seine would be clean enough to host those events — the swimming marathon and the swimming stage of the triathlon, plus a Paralympic swimming event — despite swimming in the badly contaminated river being banned 100 years ago.

To prove her point, she had promised to take a dip herself, and on Wednesday, she made good on the vow, emerging from the water in a wetsuit and goggles to proclaim it "exquisite."

Hidalgo dived in near her office at City Hall and Paris' iconic Notre Dame Cathedral, joined by 2024 Paris Olympics chief Tony Estanguet and another senior Paris official, along with members of local swimming clubs.

"The water is very, very good," she enthused from the Seine. "A little cool, but not so bad.''

Much of the pollution that has plagued the river for a century has been from wastewater that used to flow directly into the Seine whenever rainfall swelled the water level.

A mammoth $1.5 billion has been spent on efforts since 2015 to clean the river up, including a giant new underground rainwater storage tank in southeast Paris.

Last week, Paris officials said the river had been safe for swimming on "ten or eleven" of the preceding 12 days. They did not, however, share the actual test results.

A pool of reporters stood in a boat on the Seine to witness Hidalgo's demonstration of confidence in the clean-up on Wednesday.

Heavy rain over the weekend threatened to spike contaminant levels again, and water testing continued right up until Wednesday.

There is a Plan B, with alternative arrangements for the Olympic events should the Seine water prove too toxic for athletes once the games get underway on July 26, but confidence has been high, and the country's sports minister even took a dip on Saturday, declaring the water "very good."

If the Seine is fit to swim in for the Olympics, Hidalgo will have managed to accomplish a feat with her nearly decade-long cleanup project that eluded a previous effort by former Mayor Jacques Chirac (who then became French president), when he led the capital city for almost three decades from 1977.

In:
• Paris
• Olympics
• Pollution
• France

Elaine Cobbe

Elaine Cobbe is a CBS News correspondent based in Paris. A veteran journalist with more than 20 years of experience covering international events, Cobbe reports for CBS News' television, radio and digital platforms.