A spokeswoman said: “We sent an incident response officer, a motorcycle responder and an ambulance crew to the scene.
“We also dispatched London’s Air Ambulance.
“We treated a man at the scene and took him to a major trauma centre as a priority by road.”
A spokeswoman for Metropolitan Police said: “Police were called at approximately 2.05pm on Tuesday, October 16 to reports of a man who had fallen from a bridge and entered the water near Marsh Wall.
“Officers and the London Ambulance Service attended and the man was rescued from the water.
“He was taken to an east London hospital. At this stage, his condition is being treated as life threatening.”
Enquiries are continuing.