LIDO BEACH, N.Y. (CBSNewYork) — Summer is in full swing, and so is shark season.

Nassau County is increasing patrols after two days of shark sightings off the coast of Long Island, CBS2’s Carolyn Gusoff reported Friday.

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From the air, sea and sand, police have their trained eyes on ocean waters.

There was a shark sighting at Nickerson Beach on Wednesday. Two sand sharks were spotted close to the shore off Jones Beach on Thursday.

“We do run into certain situations where patrons do flag us down. They think they see something in the water, possibly a fin,” said Officer Chris Drechsel.

Nassau officials said they don’t want to frighten anyone, but shark activity off the shore is up with an unprecedented 20 sightings last year.

They’ll be looking for fins and other signs that sharks may be near.

“Maybe increase of birds or choppy activity, which might signify a feeding area. They’re looking to see if people seem in distress,” said Deputy Police Commissioner Kevin Smith.

An astonishing drone view just 200 yards off Bridgehampton clearly shows sharks are among us. So does the recent catch of a nearly 500 pound thresher shark off the Hamptons.

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TJ Minutillo catches sharks and releases them from Nassau beaches. He said some are harmless, but not all.

“Black tips, they’re all over Florida, and there’s not too many reported attacks by them,” Minutillo said. “But bull sharks, they have been known to be dangerous.”

Their numbers, along with whales and dolphins, are increasing, according to experts. It’s due in part to cleaner water and better protections, they say.

“You see increases in population. You see changes in basic abundance of these animals and distribution, and as their food source will move around, so will they,” said Rob DiGiovanni of the Atlantic Marine Conservation Society.

Along with extra patrols, officials are asking the public to be on alert. Don’t swim alone, especially at dawn or dusk. Avoid wearing shiny jewelry in the water and don’t go in the water if you’re bleeding.

“There’s so many children in the water and you just worry about them coming very close to the shore,” said one beachgoer.

“Yeah but that’s their playground. That’s the sharks’ playground, you know. That’s their home. You gotta let them breathe. That’s their life,” said another.

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If you spot a shark at the beach, officials say you should tell a lifeguard or call 911.

Carolyn Gusoff