BOSTON (CBS) – A Cape Cod harbormaster said swimmers need to change their behavior and assume there are always sharks in the area or “something terrible is going to happen.”

Nathan Sears, the natural resources manager and harbormaster in Orleans, posted on Facebook Wednesday night that the town manages the life-guarded section of Nauset Beach “under the assumption that there are always sharks in the vicinity of the swim area.”

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“The challenge is trying to convey the gravity of the situation to the beachgoers,” Sears wrote.

A shark spotted near the shore on Race Point Beach in Provincetown (Image credit: @_arianamartel_)

Sears’ warning comes after a several shark sightings throughout the summer, many close to shore. A New York man was bitten by a shark and seriously injured while swimming off the coast of Truro.

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Researchers believe sharks will continue swimming and feeding close to shore throughout the fall. Beaches are not staffed by lifeguards during fall months.

Swimmers are urged to stay close to shore at Cape Cod beaches. Still, Sears said there is a “concerning level of complacency” as people continue to swim in areas where sharks are feeding “aggressively in shockingly shallow water on an almost daily basis.”

“Fortunately, no one has died yet. However, it can only be expected that more incidents will occur if people continue to take unnecessary risks,” Sears said.

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“It is time for beachgoers to change their behavior or something terrible is going to happen. Please be safe.”