Police say the 13-year-old boy was pulled out of the lake by civilians around 5:30 p.m.
Witnesses told reporter Lucy Yang that a group of young boys may have been trying to catch a turtle when one of the youngsters found himself in trouble.
"He went a little too far and said I can't swim," Alana Thomas said. "Friends tried to help. They probably couldn't swim either. So, they couldn't go in."
Officials say both the NYPD and FDNY responded to the scene. Firefighters stripped down from their bunker gear to jump in and rescue the boy.
"Response was unreal. Fire. Police. All throwing on kit and getting in," swim instructor Annie Cooper said. "Unbelievable how quickly they responded."
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First responders immediately performed CPR on the victim, who was rushed to Methodist Hospital. He remains in critical condition.
Those familiar with Prospect Park Lake say the shoreline is deceivingly shallow. It may seem safe to go in, but the floor drops without warning, making this bucolic lake dangerously deep for those who cannot swim.
According to the Prospect Park Alliance, they warn people to "Never drink, swim or wade in any the Prospect Park Lake and other waterbodies."
There are also warning signs about the algae bloom.
The investigation is ongoing.
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