More sharks were spotted Wednesday close to the shoreline of New York's Long Island, a day after authorities closed the beach to swimmers because the 18-foot sharks were seen lurking near the water's edge.  

West Hampton Dunes Police Sgt. Tim Turner had received reports of sharks in the water on southeastern Long Island at around 3 p.m. Tuesday. There were about 50 people on the beach at the time.

The sharks were spotted within 15 feet of the shoreline. Some onlookers thought they were thresher sharks. 

On Wednesday, authorities told Fox News that they found the remains of a seal washed up on Cupsogue Beach. The seal is believed to have been eaten by the sharks.

Turner said it's not unusual to see sharks, but not so many at one time.

The beaches will remain closed to swimmers until the Suffolk County Parks Department determines it is safe to reopen them.

Fox News' Rick Leventhal and the Associated Press contributed to this report