The Seine is due to play a central role in the Games as it is due to welcome at least 140 boats carrying around 10,000 athletes for the Olympic Opening Ceremony.

It is also set to serve in triathlon, marathon swimming, and Para triathlon events.

With a few exceptions, swimming in the Seine has been off limits since 1923.

It is said that without the deadline of the Olympics, from July 26 to August 11, and Paralympics, scheduled for August 28 to September 8, the clean-up operation would not have happened so quickly.

City Hall officials claim it would have taken years to fund the effort.

"It will create waves, so to speak, across the world because a lot of cities are watching Paris," said Dan Angelescu, a scientist who is tracking the Seine's water quality for City Hall, as reported by Associated Press.

"It's the beginning of a movement.

"We hope so, at least."

An Olympic law was adopted in 2018 and gave moored boats two years to hook up to Paris' sewage network instead of emptying waste directly into the river.

More than €500 million (£439 million/$545 million) is being invested into storage basins that will reduce the need to spill wastewater into the Seine untreated when it rains.

One such facility is being dug next to Paris' Austerlitz train station and will hold the equivalent of 20 Olympic swimming pools of dirty water that will be treated instead of ending up in the river.

City Hall claims the Seine's water quality is improving and more species of fish have also appeared.

French Para triathlete Thibaut Rigaudeau finished fourth in the men's individual visually impaired event at Tokyo 2020 and is set to compete again next year.

"We will be the 'testers'," he told AP.

"I hope we don't get sick."

Following the Games, there are plans to reopen the river to the public in the French summer of 2025 with five potential bathing spots being studied in Paris.