A Hempstead lifeguard spotted a shark at Atlantic Beach around 3 p.m., while a lifeguard at Jones Beach also spotted a shark close to the shore.
The entire strip was then closed for swimming, from Jones beach to Atlantic Beach, for the rest of the day.
There were three shark sightings on Monday afternoon, with the first being a Town of Hempstead lifeguard who reported seeing a significant sized shark near a lifeguard on a surfboard.
They weren't sure of the exact size, but the shark was just eight to 10 feet away from the shore.
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The Town of Hempstead contacted Long Beach, Jones Beach and all the beaches along the south shore. Then, a second sighting happened at Long Beach followed by a third sighting in Point Lookout.
Lifeguards red-flagged the strip of water as per the New York State shark protocols, and swimming had been prohibited at certain Town of Hempstead Beaches: Civic Beach, Lido Beach, Lido West Beach, Town Park Point Lookout and Town Park at sands.
While swimmers were allowed back into the water in Hempstead later Monday, Long Beach decided to wait until Tuesday morning to reopen. Still, Hempstead beaches had allowed knee-deep wading only.
Siena Diaz was one of several swimmers who were ordered to get out.
"I noticed people backing out and I was, OK, I'm going back out too," she said. "It's a good thing I got out."
Diaz didn't see the shark, but lifeguard Logan Fitzgerald did -- and it was bigger than him.
"It shot out of the water, but definitely spun around," Fitzgerald said. "Definitely dorsal fin, that wasn't curved straight up. Not a dolphin, definitely a shark."
Another lifeguard confirmed the sighting, and identified it as a bull shark -- a species that can grow to 8 feet in length and is known to be particularly aggressive.
Authorities released a photo of a sea ray that washed up with enormous bite marks.
"By the shape of the head, shape of dorsal fin, fitness of the body, we determined it as a bull shark," Chief Town Lifeguard Mike Romano said.
The water temperature is now close to 80 degrees, and experts believe sharks are moving closer to shore in search of food.
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There have been at least 20 shark sightings in New York in the past 12 months.
With more people boating during the pandemic, the thinking is that's why there's been more reported sightings, while the actual number of sharks in the water is likely similar to previous years.
Lifeguards will continue to monitor the situation and determine when it is once again safe for swimming to resume.
Fortunately, no one was injured by the sharks.
Nassau County officials plan to use helicopters Wednesday to help check the water for any looming danger.
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