A gun was recovered by police divers from the Rochdale Canal.
The weapon was later found to be an imitation firearm.
Police said, however, enquiries were continuing and the gun had been sent off for forensic testing.
The North West branch of the Canal and River Trust alerted police after the gun was discovered and photographed on the canal bed during a recent ecological survey.
The North West Police Underwater Search and Marine Unit was called as a result.
The black handgun-shaped fake was recovered by specialist divers today.
The exact stretch of canal involved hasn't been revealed.
Images released and posted on Twitter by the unit showed the gun lying surrounded by silt on the canal bed.
They posted on Twitter: "Today we were tasked by Greater Manchester Police to search for a firearm, which had been photographed during an ecological survey on the North West branch of the Canal and River Trust's Rochdale Canal.
"An imitation firearm was recovered.
"Further enquiries and forensic tests will take place."
The find follows the discovery of a 'potentially lethal weapon' by police searching inside a communal bin store in north Manchester.
The handgun - and ammunition - was found at the rear of a block of flats on Old Market Street, Blackley.
Officers made the discovery while 'engaged in unrelated matters in the vicinity' on Tuesday, a GMP spokesman said.
The weapon has now been made safe, a police spokeswoman said.
Officers are now appealing for anyone with information to get in touch.
They are keen to chat to people in the area who have noticed anything suspicious.
Det Insp Paul Crompton said: "Thanks to the diligence of officers conducting unrelated enquiries in the area, we have uncovered and removed a potentially lethal weapon from our streets."
