Officers were called at 12:22pm on Wednesday, 3 November to Stebbing Way, Barking near Wivenhoe Road.
A body was reported to be in a waterway at the location.
Police, London Ambulance Service [LAS] and London Fire Brigade [LFB] attended and the body of a teenage boy was recovered, he was pronounced dead at the scene.
Police believe they know the identity of the deceased and are in contact with his family.
Officers await formal identification.
A post mortem examination will take place in due course.
The death is currently being treated as unexplained.
Detectives from the East Area Command Unit (EACU) investigate.
Detective Inspector Sean Treweek of EACU, said: “We are trying to understand the circumstances of how a young teenage boy lost his life. His family have been left devastated and they are looking for, and deserve, answers.
“We are particularly looking for information from anyone who was in the area Wivenhoe Road, Barking from the evening of Monday, 1 November to midday, Wednesday, 3 November. If you saw anything that could assist our investigation, whether or not you thought it was suspicious, then please call. Any information you supply could help us explain why this tragic event occurred.”
Any witnesses or anyone with any information is asked to call police on 101 or contact via Twitter @MetCC. Please quote CAD4262/03NOV
To give information anonymously contact Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.