A wayward dolphin that meandered into a polluted urban canal, riveting onlookers as it splashed around in the filthy water and shook black gunk from its snout, died Friday evening, marine experts said.

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

Marine experts had hoped high tide, beginning around 7:10 p.m., would help the dolphin leave the canal safely. But the dolphin was confirmed dead shortly before then, said the Riverhead Foundation for Marine Research and Preservation, which didn't immediately know how it died.

Earlier, with the dolphin swimming about and surfacing periodically, bundled-up onlookers took cellphone photos, and a news helicopter hovered overhead.

The New York Police Department said the marine foundation's experts had planned to help the dolphin on Saturday morning if it didn't get out of the canal during high tide. The foundation, based in Riverhead, on eastern Long Island, specializes in cases involving whales, dolphins, seals and sea turtles.

The filthy canal was named a Superfund site in 2010, meaning the government can force polluters to pay for its restoration. For more than a century before, coal yards, chemical factories and fuel refineries on the canal's banks discharged everything from tar to purple ink into the water, earning it the local nickname The Lavender Lake for its unnatural hue.

The dolphin, which appeared to be about 7 feet long, likely entered the canal from the Atlantic Ocean through the Lower and Upper New York Bays and then the Gowanus Bay, which leads to the canal. It's about 20 miles from the canal to open ocean.

It may seem strange, but it's not uncommon for sea creatures to stray into city waters, though they don't often swim away alive.

A dolphin was found dead last August near Long Island, south of the canal. Another washed up in June in the Hudson River near Manhattan's Chelsea Piers sports complex.

In 2007, a baby minke whale that briefly captivated the city wandered into the Gowanus Bay and swam aimlessly before dying.

Two years later, a humpback whale took a tour of the city's waters before leaving New York Harbor safely. The 20-foot whale was first seen in Queens before it headed for Brooklyn, took a swing through the harbor and headed toward open waters near the Verrazano-Narrows Bridge.