The long-stalled plan to build a floating pool in the East River is once again delayed.

For more than 15 years, organizers behind the +POOL project have worked to design and build a pool that filters water from the filthy waterway to make it clean enough for swimming.

A prototype pool meant to test the viability of a final version of the project was slated to hit the East River off of Manhattan this summer, two years after Gov. Kathy Hochul and previous Mayor Eric Adams pledged a combined $16 million for the project.

But that isn’t happening.

The +POOL team announced Wednesday that the launch of the prototype is being pushed back until at least 2027 due to a scheduling conflict with the city’s ongoing work to prevent flooding from future storms. The pool’s testing site sits right in the middle of a major project to protect the city from future floods — where work has stepped up in recent weeks.

The original renderings for the plan showed a plus-symbol-shaped floating pool so beautiful it would beckon swimmers from across the city to the shores of the East River in Lower Manhattan. The team behind the idea started holding fundraisers for the project in 2010. It has proven so elusive to realize that the saga has dragged on into a fourth mayoral administration.

“Our primary responsibility, as stewards of such a large-scale, publicly funded project, is to pivot when necessary to support the needs of our city and state partners, investors, and the people of New York,” Kara Meyer, managing director for Friends of + POOL, wrote in a statement. “While this shift comes at a cost to the organization and the project, those realities will feel insignificant when we are living in a New York City that has advanced infrastructure to protect from storm surges while opening up safe public river access for healthful recreation.”

The project has faced other setbacks, including gobs of seaweed that gummed up the system’s test filters and concerns from the city’s health department about how safe it would be to have people swimming in water in such close proximity to sewage outlets.

The prototype pool is nearly complete and sits moored at the Erie Basin Bargeport in Red Hook, from where it will be eventually towed into place along the Manhattan shore, according to the project's organizers.

The organizers said they have also successfully secured all their required approvals from city, state and federal agencies for the eventual testing phase next year.