Subtitles section Play video
The mayor of Paris, Anne Hidalgo, has been swimming in the Seine to prove it's safe.
The river is scheduled to be used for a number of events in the Olympics, which begin next week.
But heavy rainfall has resulted in higher levels of pollution in the water.
Our Paris correspondent, Hugh Schofield, reports. A big day for Paris, a big relief for the Olympics.
After weeks of tests showing bacteria levels in the River Seine to be unacceptably high, with impeccable timing, things have come good.
The city mayor, Anne Hidalgo, led the way.
She made a vow to take a swim in front of the cameras to show to the world that the river once again is safe. "It's a very lucky and happy day.
It's also for the planet, you know, and for the river and for the ocean.
We did it.
We did it." A select group was invited to join the swim.
One among them, your correspondent. "OK, here goes.
I'm going to jump.
Ready?
One, two, three." Quite a privilege.
Apart from a few experiments in advance of the Olympics, this is the first legal swim here for more than a century. "Good stuff.
I got a mouthful of water as I jumped in.
But it tastes fine.
Everything seems to be pretty cool.
The water is gorgeous.
A bit murky, but it feels good.
And it's not cold at all.
I think we're well set up for the Olympics." Some members of swimming clubs were also invited. "It was really cool and really nice to swim in Paris in the Seine.
It's the first time, and we are the first to swim, so it's really, really amazing.
The city of Paris was born here, born with the river Seine.
So we try to show that it's our natural system, our natural place to be here." What it all means is that Olympic swimming events scheduled for the Seine should now go ahead as planned.
And beyond that, this will be one of the big legacies of the Games: open-air bathing once again in the middle of Paris.
Hugh Schofield, BBC News, Paris.