Open verdict after grim find.
Majid Rajaby, 31, of Meath Street, Middlesbrough, was discovered by dog walkers at Riverside Industrial Park, Stockton, on January 15 this year.
An inquest into his death was held at Teesside Coroner's Court where coroner Michael Sheffield recorded an open verdict into the death.
Darren Brannigan, 38, of West Lane, Middlesbrough, told the inquest how he and a friend discovered Mr Rajaby's body.
He said as they walked his friend's dog was trying to get through the railings at the edge of the river.
He said: "I looked down towards the edge of the river and could see what appeared to be a human body lying face down."
Nicole Clark, a specialist addiction nurse at Fulcrum Medical Practice said in a statement Mr Rajaby, an Iraqi national, struggled with drug addiction and had been in and out of prison.
She said he had been on methadone and despite attempts to stay off heroin, would often restart his drug use.
Saaid Amiri, who lived with Mr Rajaby, said in a statement he had not been worried about him and did not think he was "suicidal."
Pathologist Dr Mark Egan gave the cause of death as drowning and methadone and diphenhydramine toxicity. Coroner Michael Sheffield said it would be a matter of speculation as to why Mr Rajaby inhaled water from the River Tees and why he was in the place he was found.
He said: "It is unlikely anyone else was involved but that would be speculation.
"As it is impossible to speculate, I am returning an open verdict."