Police have admitted some people have been pushed into Manchester's waterways, but deny there is a serial killer at large.
Over the last six years 85 people, mostly men, have died in the city's waterways, and 28 deaths remain unexplained.
The figures, made public in January last year, have prompted claims that there is a serial killer dubbed "The Pusher" in the city.
Detective Superintendent Peter Marsh, of the major incident team, said in a statement released in response to the serial killer rumours that each death has been fully investigated.
He said: "The purpose of our investigation is to identify if there is anything criminal that has happened to the individual. In the case of someone that goes into a canal or water - have they been pushed, have they been assaulted, have they been robbed?
"Some of these have been as a result of people being pushed and robbed, and people have been arrested and prosecuted."
During a Channel 4 documentary, Greater Manchester Police reveal one particularly problematic 400-metre stretch of underground canal.
With four deaths in the area in the last six years, and a further five in the locks either side, officers said the incidents have been put down to drunk individuals falling in and robberies going wrong.
Every time a body is pulled from the waterways in Manchester, rumours of The Pusher resurface - something the police have repeatedly denied.
Mr Marsh said the force has a high detection rate for murders and manslaughters and any new evidence presented to them will be investigated, but there is "no evidence to support" the serial killer theory.
"If a person has pushed someone into a canal and we have been able to investigate it, that person has been traced, they have been interviewed - and on one such occasion one of these individuals has been interviewed, CPS have offered no charges because of the circumstances around it and no prosecution has ensued," he said in the statement.
During the hour-long documentary, he said he and other officers have reviewed the deaths.
He said: "The reason we have looked at these is to give the families more reassurance that there is no evidence to support the theory there is a serial killer at large.
"Most of those bodies, there is a definitive explanation behind it. Some people have gone swimming, we have got people seen staggering home, walking along the canal and falling in."
In a statement at the end of the programme, Greater Manchester Police said: "Each death has been subject to significant investigation and independently scrutinised by the coroner. There have been no verdicts of unlawful killing in these cases."
:: The documentary, Manchester's Serial Killer?, is on Channel 4 at 11pm on Tuesday.