Officials have closed down Nauset Beach because of a confirmed sighting of a great white shark.
The Cape Cod Times reports that Orleans Harbormaster Dawson Farber said a senior Orleans town lifeguard spotted a dorsal fin about 150 yards off the beach at about 10:15 a.m. Sunday.
He says the shark was estimated to be between 12 feet and 13 feet long.
Swimmers were asked to get out of the water and surrounding towns and the Cape Cod National Seashore were notified.
The shark was seen toward southern end of protected swimming area and headed in the direction of Chatham.
Swimmers must be kept out of the water for an hour after a confirmed sighting unless there is another sighting.