It was not something you'd see in Brooklyn every day.

Cellphone video showed more than a dozen rays swimming along Newtown Creek in Greenpoint.

Willis Elkins, executive director of the Newtown Creek Alliance, said the group was believed to be cownose rays. A group of rays is called a "fever."

"This is really, really special," said Elkins.

Elkins said it was a rare sight to see along the waterway, which is a designated superfund site.

"You have 150 years of industrial toxins that were dumped into the waterway or leached in from the shoreline," said Elkins.

But Elkins said seeing the rays in Newtown Creek was an indication that the water quality is improving.

"We still have big issues," said Elkins. "When it rains, we still get untreated sewage being discharged to all of New York City waterways. So, there's still a lot of work to do there, but we still have made a lot of progress compared to 30 years ago."

Elkins added that in his 13 years with the alliance, he had never heard of rays swimming in Newtown Creek.

"It's really an amazing sight to see," he said.