If I still lived in New York, I would definitely be contributing to +Pool on Kickstarter. This would be an unbelievably awesome asset for New York (particularly Brooklyn!), and with its simple + shape (which I love), I think it would become a new design icon for the city!
The concept is simple: build a pool right in the East River that filters river water through the pool walls make it clean for swimming.
PS: +Pool, once you finish this project, I propose you come out to San Francisco and start working on a pool that floats in the Bay and heats the water as it passes through the filtration system!