Bomb disposal experts had to be drafted in after 'suspicious items' were pulled from the water by a magnet fisherman.
Police were called to the Bridgewater Canal, just off Chester Road in Stretford, Trafford, just before 2.30pm on Sunday afternoon.
The area was taped off for several hours while the find was examined by explosive experts.
The items were then taken by the bomb disposal unit to nearby Turn Moss Playing Fields where a controlled explosion was carried out at around 6pm.
Inspector Abbott at the scene told the Manchester Evening News that one of the items was believed to be a one-pound artillery shell.
The other was another magnet.
He said experts decided to carry out the controlled explosion because they were unsure it could be safely transported.
It was unclear how old the war time ammunition was, but it was 'very wet and rusty'.
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A GMP spokesman added: "Police were called at 2.25pm to the canal to reports a fisherman had located some suspicious items.
"EOD attended and were due to carry out a controlled explosion."
It's not the first time bizarre items have been discovered by magnet fishermen.
In February, a safe stolen during an armed robbery more than a decade ago was found in the Rochdale Canal.
Scott Bryant made the find while magnet fishing in the stretch of water near Manchester Road in Castleton.
Inside, he found a number of watches, jewellery and an old driving licence with owner Robert Teale's name on it.
The 38-year-old then tracked down Robert on Facebook and returned everything to him.
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