Onlookers spotted a dolphin swimming near West 14th Street and the Hudson River on Sunday. View Full Caption Jennifer Parker

CHELSEA — It's SeaWorld in Manhattan.

A dolphin was spotted in the Hudson Sunday afternoon, delighting onlookers who happened to catch the rare sighting as it made its way from Harlem to Chelsea.

The Riverhead Foundation for Marine Research and Preservation, which monitors marine mammals in New York, said it began to hear about the dolphin at 2 p.m. when it was near West 120th Street. A few hours later, at about 4:30 p.m., Jennifer Parker spotted the dolphin near West 14th Street.

"It was right there, by the pier," she said. "It kept swimming around in a loop in the area for the half hour I was there."

Kim Durham, the director of the Riverhead Foundation's Rescue Program, said the dolphin in the pictures looked like a bottlenose.

"Typically, the furthest north they go is New Jersey," she said.

The foundation has found dolphins as far up the river as Albany, but that one was hurt and the Hudson's water had harmed it skin, Durham said.

She added that bottlenose dolphins often travel in groups and one by itself was unusual, but it was not immediately clear if the animal was behaving like it needed help.

"A lone dolphin does kind of have us on alert," she said.

"The main thing we look for is whether or not it's free swimming or if it comes ashore."

Durham said that anyone else who sights the dolphin should immediately contact the foundation's 24-hour stranding hotline at 631-369-9829.