NEW YORK (AP) - A wayward dolphin that swam into a polluted New York City canal has died.

The Riverhead Foundation for Marine Research and Preservation says the dolphin died Friday evening. It doesn't know how the dolphin died.

In frigid weather, the dolphin wandered into the Gowanus Canal earlier Friday.

The dolphin appeared to be about 7 feet long. It surfaced periodically and shook black gunk from its snout in the dirty water.

Experts had hoped the dolphin would free itself from the area during the evening's high tide.

Friday's deep-freeze weather didn't seem to faze the dolphin as it swam around in the Gowanus Canal, which runs 1.5 miles through a narrow industrial zone near some of Brooklyn's wealthiest neighborhoods.

Bundled-up onlookers took cellphone photos. A news helicopter hovered overhead.

The filthy canal was named a Superfund site in 2010, meaning the government can force polluters to pay for its restoration.