Thanks to Architectural Digest for this:
+ Pool is an initiative between Family New York and PlayLab to build a floating, self-filtering pool in the rivers of New York City. The project was launched with the ambition to improve the use of the city’s natural resources by providing a clean and safe way for the public to swim in New York’s waters.
A group of four innovative friends is calling for a serious cleanup job by way of a giant plus sign–shaped floating pool (after the group’s name, + POOL) just north of the Manhattan Bridge, which connects Manhattan’s East Village neighborhood to Brooklyn’s Dumbo.
Without any chemicals and additives, the pool filters more than 600,000 gallons of East River water daily. 
Floating Pool NYCArchie Lee Coates IV and Jeff Franklin of the design firm PlayLab, and Dong-Ping Wong and Oana Stanescu of the architecture firm Family, originally conceived of the idea for + POOL back in 2010, but like anything worth doing, it took a while to actually become a reality. After all, the group had to (and continues to) raise funds, develop working filtration systems, and test them for accuracy and efficiency. And after years of research and testing, the four friends have managed to prove that + POOL’s tech actually works.
And now that the city has allowed + POOL to officially drop anchor in a specific location, the real challenge begins: raising between $20 million and $25 million to give New Yorkers the Olympic-size warm weather haven they’ve been dreaming of for years.
Now that + POOL has an official home in the East River, eager New Yorkers may be one step closer to fearlessly diving into the salty water, but it’s still a little ways off, considering construction could take up to two years.
+POOL homepage
