Hundreds of beachgoers were ordered out of the water Monday afternoon when a great white shark was spotted cruising just outside the buoys delineating the swimming area at Duxbury Beach, officials said.
The shark was spotted by a State Police helicopter on the ocean side of the beach at about 2 p.m., said Duxbury Deputy Fire Chief Chris West. All swimmers were cleared from the water following the sighting, officials said.
State Police monitored the great white from a helicopter. Duxbury Fire Chief Kevin Nord said two local harbormaster boats surrounded the shark in an effort to force it out of the area.
Shortly before 4 p.m., officials said the beach had been reopened, but people were advised only to go in up to their waists, and that they were swimming at their own risk.
A scientist from the state Division of Marine Fisheries examined photos of the shark and confirmed it was a great white, State Police said.
The shark was spotted on a routine patrol by Air 2, one of the State Police's helicopters, said spokesman David Procopio. The shark, estimated to be 12 to 14 feet long, was 75 to 100 yards offshore, he said.
State Police then contacted authorities in Duxbury, Procopio said.
Nord said with about 1,000 beachgoers in the area, the shark was "too close for comfort."
Nord said there have been sightings of smaller fish in the area, but the shark spotted Monday was "the biggest we've seen" this year.
Edward Rose, 40, of Duxbury, said he was on the beach with his family when he saw a shadow of the shark's head. He said he thought it was about 50 yards off the beach.
"We were sitting next to this woman and kid who were fishing, and next thing we knew, we heard the zing of their fishing string, saw the rod get bogged down, and then saw the pole get pulled into the water within three seconds," Rose said. "It was unbelievable."
Rose's 8-year-old son, Hutchison, said he was swimming near the shore with his 6-year-old sister and a couple other friends when their parents started yelling at them to get out of the water.
"It was crazy because I was right there in the water, and I started to get nervous when I saw the [fishing] line snap," Hutchison Rose said. "It was pretty cool."
He said he did not immediately realize it was a shark when he was in the water, but if he had, he said he "would have just ran as fast as I could."
Monday's shark sighting was the second off the Massachusetts coast in two days.
A great white was spotted swimming about 115 yards off a Wellfleet beach Sunday morning, officials said. The lifeguard who spotted the shark said it was an estimated 10 to 12 feet in length and was heading southeast, said Wellfleet police Lieutenant Michael Hurley.
Duxbury is an unusual place for a great white sighting, said Amy Mahler, a spokeswoman for the Department of Fish and Game.
Mahler said there have been more than a dozen shark sightings off the coast of Massachusetts this summer.
Mahler said one factor in the increase in shark sightings in recent years can be attributed to an increase in the gray seal population, a favorite food for sharks. "With the increase in protection over marine mammals in the past 40 years, the gray seal population has rebounded," Mahler said. "As a result, there is strong evidence to suggest that great white sharks have increased their predatation on these animals."
Below is an image of the beach in Duxbury.