The Cedar Grove Police Department said a group of people went into the water in Cedar Grove, New Jersey, despite seeing "no trespassing" signs posted and warnings about the risks of swimming in the area.
They say someone went into the water and failed to resurface.
Police, firefighters and many surrounding agencies responded to the scene after 5:15 p.m.
An 18-year-old male was pulled from the water unconscious.
He was pronounced dead at the hospital.
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