Police were called to reports that a child was in the River Irwell in Radcliffe, Greater Manchester, shortly before 4.25pm on Wednesday.
The child, whose age has not been confirmed, was rescued after emergency services attended the scene and was taken to hospital where he is in a critical condition.
The baby was reportedly thrown into the water from a bridge. Eyewitnesses said that two fire engines, ambulances, multiple police vehicles and the GMP force helicopter were at the area, according to the Manchester Evening News.
Greater Manchester police tweeted: “Police are currently responding to an incident in #Radcliffe.”
“Shortly before 4.25pm (Wednesday 11 September 2019), police were called to reports that a child was in the River Irwell.”
A spokeswoman for Greater Manchester Police said: “A man has been arrested on suspicion of attempted murder. He remains in custody for questioning.
“An investigation is under way and enquiries are ongoing.”