Two great white sharks were spotted off Cape Cod on Friday, just as thousands of people were preparing to head for the beach for Labor Day weekend.
According to the Sharktivity app, one shark was spotted off Wellfleet, and the other off Chatham.
Cynthia Wigren, executive director of the Atlantic White Shark Conservancy, said both sharks were close to shore.
"The one off North Beach Island in Chatham was 20 yards offshore," she said. "The beach was fairly quiet, though, and it's not a beach with a lifeguard."
Wigren said she's not sure if the lifeguards at Wellfleet Beach pulled swimmers out of the water as a result of the shark sighting there.
Experts say great whites have been moving further north in recent weeks, which has forced the closure of several beaches to swimming.
On Wednesday, two beaches in Eastham were temporarily closed to swimming after two great white sharks were spotted - one of them eating a seal.
Last weekend, Race Point Beach in Provincetown was shut down for a time, and seven sharks were spotted off Nauset Beach on Aug. 18.
Wigren said there is no new advice for beachgoers, but anyone hitting the beaches on Cape Cod should be aware that sharks are present along the coast. She urged beachgoers to pat attention to signs and flags and listen to the lifeguards.