No, this is not a joke – you can actually jump in if you dare.
The day of open-air swimming in the city's largest official lake has been organized by the French Swimming Federation (FFN), for those willing to brave the somewhat murky waters.
“People don't really know much about open water swimming, but I think a lot of people would like to try it,” a spokesperson from the FNN told The Local.
“This is a good thing for Paris.”
The day of swimming and races will be held in the Bassin de la Villette, which connects the Canal de l'Ourcq with the Canal Saint-Martin in the 19th arrondissement.
Official races will be held until 3pm, and then the public is invited to take a dip for free up until 6pm.
Normally it's illegal to swim in the lake, although that hasn't stopped some from taking the plunge during the current heatwave. In fact, in front of The Local's offices at the time of writing, people can be seen cooling off in the bassin with little regard for the rules.
The spot is popular for boating in the summer, however some might be wary about actually getting into the water.
A massive clean-up operation in the Canal Saint-Martin recently uncovered a variety of bizarre objects hidden in its depths – from bottles to bikes to a stray toilet – but organizers promise the water in the Bassin de la Villette is safe for Sunday's event.
The FNN said the water had been analyzed on Thursday, and that a second test would be carried out on Friday to make sure it was clean. However, as a precautionary measure, under 18s have been banned from taking part.
Adventurous swimmers can sign up through the FNN's website, but competition will be tough, with France's 2016 Olympic swimming team also taking to the waters. Hundreds have already signed up for the races, and in total over 1,600 people have shown interest on the Facebook event page.
Continuing the Olympic theme, the event is also linked to the city's bid to host the 2024 Games; Paris mayor Anne Hidalgo has suggested that the swimming section of the triathlon could take place in the Seine. In June, she launched a plan to make open water swimming possible in several areas around the city, including the Bassin de la Villette, by 2017.
You might not guess it looking at the water today, but swimming in the city's lakes and river was a common past-time up until the 60s, even though it was officially banned by the prefecture in 1923. Fears over dirty water as well as an increase in boat traffic saw the hobby become much less popular.
Sunday's event is called La Fluctuat – a reference to the city's motto, 'Fluctuat nec mergitur'.
The French aren't strangers to jumping in the bassin as the video below shows, with people plunging into the water from the bridge during a heatwave last year.