A 15-year-old boy died over the weekend after entering the waters off Sandy Hook Beach in New Jersey.
Gateway National Recreation Area's Daphne Yun told Fox News Digital in an email on Monday that six people had been rescued from Beach B, which is a non-lifeguarded beach.
Two of the beachgoers were transported to Jersey Shore University Medical Center and three others were transported to Monmouth Medical Center.
The teenager was among those three and was pronounced dead after arrival. He was not immediately identified.
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One of the individuals refused to receive medical attention.
Yun reportedly told NJ.com that the conditions of the victims were not immediately known after the incident at around 4:30 p.m. ET, and that there had been signs indicating there is no lifeguard on duty at the beach.
Swimming at Beach B is not allowed, as is detailed on the National Park Service website.
Witnesses told ABC 7 they heard a mother cry that she could not see her son in the surf on Sunday.
"They pulled him out, they started giving him CPR, and they couldn't get him back," added Luis Sanchez.
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"When it's windy. The weather is like this – you get rip tides, and you can easily drown," he said.
The National Weather Service in Mount Holly warned beachgoers to be "extra cautious" on Monday if going into the water due to a "HIGH risk or rip currents."
"Be safe & only swim with a lifeguard present," it said.
It had warned about the risk of rip currents off the shore starting on Friday.
Swimming is only permitted at C, D, E, Gunnison and North beaches, which are guarded. Those beaches have lifeguards from 10 a.m. to 6 p.m. ET.
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Swimming beaches are open from Memorial Day weekend through Labor Day.
"From Memorial Day weekend through Labor Day weekend this is the first parking lot visitors will approach while heading into Sandy Hook," the agency noted of Beach B.
Last year, nearly 30 people drowned in natural waters in New Jersey, according to preliminary data from the state Department of Health.