NYPD officials say a male, about 18 years of age, jumped over a railing at Pier 76 near 34th Street and 12th Avenue just before 4 p.m.
They say the victim immediately began yelling for help.
Police say NYPD Scuba and Aviation responded to the location.
Two divers jumped into the water, frantically searching the river for the victim as FDNY rescue boats attended nearby.
In about 15 minutes, divers found the victim and brought him to a waiting NYPD boat, which took him to shore and eventually an ambulance.
The NYPD says the victim was taken to Mount Sinai West in critical condition.
There's no word yet on what led him to jump into the water.
The investigation is ongoing.
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