On Tuesday night, Brooklyn’s Wythe Hotel was the site of an unlikely pool party—specifically, a gala to celebrate the final research phase for + POOL, a four-year initiative to build a floating, water-filtering pool in New York’s Hudson or East River. Guests including architects Bjarke Ingels and Dominic Leong, restaurateur and hotelier Andrew Tarlow, artist Mike Perry, and Brooklyn borough deputy president Diana Reyna gathered to hear updates on the unique structure, which will use a series of filters to transform New York’s famously dirty river water into something fit to paddle around in while enjoying the surrounding urban views.

The project began as a Facebook post by + POOL’s original members Archie Lee Coates IV, Jeffrey Franklin, Oana Stanescu, and Dong-Ping Wong in 2010, and quickly turned into a Kickstarter campaign in 2011 and then another in 2013 that raised more than a quarter-million dollars. During that time, + POOL—in collaboration with Arup, Persak & Wurmfeld, Lamont-Doherty Earth Observatory, River Project, and other groups—refined a three-part filtration system that could feed river water into two floating Olympic-size pools and then out through an additional set of filters, ensuring that the water returning to the river is much cleaner than it was when it first entered.

With Float Lab, + POOL put its device to the test during a five-month span in 2014. The experiment, which took place in the Hudson River, was a success: The filtration process was found to have safely removed various contaminants and bacteria from the river to meet, and at times surpass, New York’s standard for swimmable water.

According to Kara Meyer, + POOL deputy director, the technology is in the final phase of research. “We are now meeting with city and state officials,” she says, “to discuss regulatory issues from what to do with the space during winter months”—one suggestion is to enclose the pool and use solar energy to heat it—“to the issue of fish shading [the dilemma of water-floating structures’ covering sunlight from marine life] to the question of whether or not to tether the floating pool to the river floor.” They likely will, she notes.

Plans for completing the first + POOL will be announced in 2016, yet that hasn’t slowed interest from places outside of New York City. As Meyer says, “other domestic and international cities, including Sydney, Cape Town, and London, have expressed interest in our eco-friendly swimming pools.” The group believes the final stages of development will take another four or five years before completion, but when it happens, New Yorkers will be able to swim in their rivers for the first time in ages.