The Medical Examiner is working to determine the baby's cause of death.
Tourists from Oklahoma made the disturbing discovery and waved police down around 4 p.m. Sunday.
A family of tourists from Oklahoma had just finished a Statute of Liberty tour in Lower Manhattan when they saw what they at first thought may have been a doll in the East River.
No parent or guardian was present at the scene and the child showed no signs of trauma, police said.
He said the baby wasn't breathing and showed no pulse.
He had went into the water "mid-thigh level", AP reports, to retrieve the baby and started CPR.More news: Luxury yacht linked to 1MDB scandal arrives in Malaysia
More news: Fetus discovered on plane from Charlotte to NY
More news: Twitter CEO: Alex Jones 'hasn’t violated our rules'
Diana Campbell posted a news story about the incident on her Facebook, adding, "Asking for prayers for this attractive baby boy. someone out there knows what might have happen to him". The child is believed to have been approximately 8 months old.
Her husband, Monte Campbell, who is a chiropractor, told the Times he called 911 and that when he was put on hold he decided to make sure it was a real baby and not a doll. She said the baby was floating about 30 feet offshore.
"Someone knows that child", she told the Times.
The boy was pronounced dead at NY Downtown Hospital.
One of them brought the baby to shore to wait for police. "It's just unreal, you don't come to the city expecting to see things like this, to see babies floating in the water".