All swimmers were ordered out of the water just after 2 p.m. Monday after the spotting near Powder Point Bridge. By 2:10 p.m., everyone was out of the water and people were being advised to stay out for at least the next hour or so.
"This is the first time that we have had a shark sighting in these waters," said Victoria Moore, a lifeguard at the beach.
Moore says it was about 600 yards off shore.
"It was coming in close," she said, and the harbor master told her to order everyone out, for safety reasons.
People on shore saw the helicopter, and knew something was up.
"All of a sudden, it's like, 'wait a minute, something's going on here,'" said one beachgoer.
Usually, Great White sightings are on the other side of Cape Cod Bay.
At around 2:40 p.m., the police helicopter was following the shark south as it swam toward deeper water. By 3:15 p.m., the helicopter cleared out of the area, and at around 4 p.m. officials announced that the beach was open and swimmers could return at their own risk.
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