Senior Coroner Kevin McLoughlin ruled that the cause of plant driver Stephen Pollard's death was unascertained before recording an open verdict after the inquest at Wakefield heard mystery continues to surround what happened to him.
Members of Mr Pollard's family told the inquest he was "terrified of water" and couldn't swim.
Mr Pollard, of Newton Lane, Outwood, had been on police bail after being arrested on suspicion of drug dealing.
The inquest heard police had arrested a number of people on suspicion of murdering Mr Pollard during an investigation following his disappearence.
Mr Pollard was only wearing underpants and one sock when his body was spotted by a dog walker on the banks of the River Aire near Beal on May 22 2015.
Forensic pathologist Jennifer Bolton, who carried out a post mortem, said the body had been in the water for a number of weeks.
She said there were no signs of injuries and said that the cause of Mr Pollard's death was "consistent with drowning" but that she could not be definite.
He was last seen by his son on David on February 19 2015 and was reported missing to police on February 22.
Detective Superinendent Nicholas Wallen of West Yorkshire Police said Mr Pollard's Mazda car was found parked on Balk Lane near the River Aire at at Stanley in Wakefield on March 2 2015.
A half-drunk bottle of spirits, a newly-bought washing line and some non prescription tablets were found in the car.
The inquest heard Mr Pollard had been arrested on suspicion of supplying drugs and was on police bail when he went missing.
Det Supt Wallen said that in July 2015 police received information that Mr Pollard may have been involved in a dispute with criminals over the alleged theft of money from a drug dealer and that he had been attacked and killed.
Det Supt Wallen said investigations revealed Mr Pollard's car and mobile phone had travelled on the A64 between York and Leeds on February 19.
He told the inquest that police had made a number of arrests and carried out extensive interviews and investigations, but had no evidence to suggest Mr Pollard had been deliberately harmed.
Det Supt Wallen said police had worked on four theories on what happened to Mr Pollard, including one that he was murdered by drug dealers and his body dumped in the river.
A second was that he died after suffering a medical episode while in dispute with drug dealers before his body was dumped in the river.
A third police theory was that he had committed suicide by drowning and a fourth was that he went in the river to retrieve an item on someone else's behalf and was swept away.
Det Supt Wallen said: "Sadly I cannot provide the court with an outcome that I can say definitely occured."
He added: "As far as I can possible say, I do not believe that Stephen has been murdered."
He said police would look at any new information that may come to light at a future date that may take the case further.
Coroner Kevin McLoughlin said a report from Mr Pollard's GP revealed that he had been undergoing treatment for depression.
Recording the cause of death as unascertained and an open verdict, Mr McLoughlin said: "It means the final report will say that the evidence doesn't enable us to say what happened."