Cue the ominous theme music.
Visitors to Zach's Bay in Jones Beach State Park were banned from swimming after a shark sighting on Thursday morning.
George Gorman, deputy regional director for the state parks, said the fish was believed to be a thresher shark, about 4 to 6 feet long.
He said the bay had about 20 people there at the time. Authorities surveying the area turned up no signs of the animal, and Gorman said it appeared to have left. The bay is scheduled to be reopened for swimming on Friday morning.
A 5-foot thresher shark washed up on a city beach in September.