It's a hot summer day, and 8-year-old Zak Ballenger and his 5-year-old sister, Alison, are doing something they've never done in Paris.
They're diving into the cold, murky waters of a city canal.
"I like splashing around," Zak says, "because it's hot outside."
His mom, Celina Ballenger, is a 38-year-old nurse. She says she couldn't afford a vacation this year.
"So we've come here because we can't go out of Paris," she says.
The Paris municipality opened the Canal de L'Ourcq last month to swimmers for the first time in recent memory. Mayor Anne Hidalgo says she's long dreamed about opening designated swimming areas here.
"This opens a door to swim in Paris's open waters," she told reporters. "In 2019, we will have swimming in the Mesnil Lake (in the Parc de Vincennes). And before 2024 we will have three pools in the Seine for swimming."
Hidalgo has set 2024 — the year Paris is expected to host the Olympics — as the deadline to make spots in the city's most famous waterway safe enough to swim.
Former Mayor Jacques Chirac made similar promises in 1988. But it's been illegal to swim in the iconic river since 1923 because of water quality and river traffic.
A 35-year-old man died in June after voluntarily jumping into the Seine during the annual Fête de la Musique music festival.
French journalist Julie Pacaud says she's jumped in as a member of the Laboratory of Experimental Urban Swimming, a collective that's seeking to "reclaim" urban waterways.
"There are a lot places where the current (in the Seine) is really strong," Pacaud says. "So it's a lot more complicated than canal swimming. And, anyway, five minutes after we jumped in, the river patrol came."
Pacaud says the canals are more relaxing.
"It's nice to float on your back to see the architecture and the urban space around," she says. "It's another way to experience the city."
Jean-Francois Dumont, a lifeguard who manages the two municipal pools — one shallow, the other deeper — in the Canal de L'Ourcq, says they give Paris "an image of being a bit less polluted, that it's more green. It took a long time to treat and clean the water."
Canal water can get polluted. When the Canal St. Martin was drained last year so it could be cleaned, municipal officials pulled out 40 tons of waste, including bicycles, toilet bowls, suitcases, chairs, shopping carts, scooters and even a car.
City officials monitor the water every day. They closed it briefly last month after finding abnormal levels of bacteria.
Yet the swimmers returned in force when the pools re-opened. Entrance is free.
Jenna Bachman, a French teacher from Denver, says she's thrilled to find a place where she and her 6-year-old son, Quincy, can enjoy a special part of Paris.
"We come to Paris every year for a month," she says. "Swimming here in the canal is another way to experience the city. And it's free, so it doesn't get any better than that."
Bachman is in a swimsuit, like many parents wading with young children in the crowded kiddie pool.
Teacher Kagni Drame, a 28-year-old native Parisian, is dipping her feet in, a towel wrapped around her chic dress. She's with her cousins, three little boys, ages 6 and 8.
"It's like you're not in Paris when you're here," she says. "You are at the seashore or something like that. But the water is a bit cold." She points to the 8-year-old, his teeth chattering.
At the neighboring deeper pool, Bart Koetsier climbs out after swimming 30 laps. The 41-year-old Dutch photographer has lived in Paris for three years and swims in indoor pools every day.
"There aren't too many open-air pools, so this canal is spectacular," he says.
Koetsier also swam here last year when the municipality allowed a race to be held here, and wants to swim in the Seine.
If people swam in canals and the river, he says, maybe they would think twice about what they throw into the water.
"It tells a little story," he says, "about how this city's changing."
Reporter Jake Cigainero contributed to this story.