York officials on Monday placed town beaches under a cautionary advisory after a shark sighting off Long Sands Beach.

A video of the shark taken by people fishing shows the large animal swimming at the surface near a boat, not far from the popular town beach. The fish was identified as a basking shark by Dr. James Sulikowski of the University of New England, according to police.

Basking sharks are common along the Maine coast. They are harmless, but are a large species sometimes confused with the more rare and dangerous Great White.

After the York Parks and Recreation Department and York police were notified of the sighting, officials placed the beaches under a cautionary advisory (yellow flag).

“We appreciate the public’s vigilance in reporting such sightings and would encourage you to continue that vigilance as you enjoy the ocean and beaches this summer,” police said in a Facebook post.

The basking shark is the second-largest fish on the planet. It can grow more than 25 feet in length, lives on a plankton diet and is not aggressive or dangerous to humans.

Last year, the National Oceanic and Atmospheric Administration reported groups of 30 to 1,400 basking sharks had been seen in waters from Nova Scotia to Long Island, New York. Sightings of basking sharks are not uncommon, but seeing them in large groups is not, the agency said at the time.