Authorities say the approximately eight-month-old child was spotted floating in the river near 89 South St. just after 2 p.m.
The Associated Press says Monte Campbell's wife, Diana, first noticed the child. "And I was like, 'Come get the baby out of the water, '" she said.
The body was spotted in the water of the East River under the Brooklyn Bridge by a family who had travelled from Oklahoma to NY for a holiday.
The baby was pronounced dead at New York-Presbyterian/Lower Manhattan Hospital, the Times reported. "I called 911. At that point I thought it was a doll", Mr. Campbell told the AP.
Her husband Monte called emergency services before reaching into the water to retrieve the boy.
A New York Police Department officer stands guard as authorities investigate the death of a baby boy who was found floating in the water near the Broo
He and police officers called to the scene gave the baby CPR until an ambulance arrived, NY media reported.
Austin Campbell, who was visiting the area with his family, said his father jumped into the river with hopes of saving the young child. The eyewitness also said it did not appear that the baby fell in from the shore.
The good Samaritan performed CPR until officers arrived on scene, police said. The medical examiner will work to determine his exact cause of death.
The East River running between Manhattan and Brooklyn is a heavily trafficked tidal estuary subject to strong currents.
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