Shark Briefly Forces Massachusetts Beach-Goers Out of Water

Great White Shark Swims Near Massachusetts' Coast 0:40

A shark sighting prompted authorities to order swimmers out of the water for about two hours at a Massachusetts beach Monday. State police told NBC News that what looked like a 15-foot-long great white was spotted by a patrol helicopter near Duxbury just moments after a crew member said, "I wonder if we can find a shark off the coast during our patrol."

State police later tweeted that the shark had likely moved to deeper waters. The beach was reopened at 4 p.m. ET, with local authorities warning, "Swim at your own risk." At least four great whites were spotted off the coast of Cape Cod, just 40 miles south of Duxbury, a week before Monday's sighting, according to NBC-affiliated New England Cable News.

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— Elisha Fieldstadt and Tom Winter