The Royal Canadian Navy is to investigate an object found by a diver, which could be a “lost nuke” missing off the coast of Canada since 1950.

Sean Smyrichinsky discovered it while he was out looking for fish near Haida Gwaii, British Columbia.

It is believed it could be a dummy nuclear weapon – but potentially still loaded with TNT – lost after a training flight crashed in the area, ditching its deadly cargo into the sea.

“I found something that I’d never ever seen before,” Mr Smyrichinsky told the CBC. “It resembled, like, a bagel cut in half, and then around the bagel these balls all cut into it, moulded into it… It was the strangest thing that I had ever seen.”

Mr Smyrichinsky was baffled by his find, which he sketched on a napkin, and initially speculated it could have been a UFO. However, when he mentioned it to an old fisherman from the area, he said it could be a bomb missing for over half a century.

On 13 February 1950, three of the engines of a US Air Force B-36 bomber aircraft caught fire while travelling from Alaska to Texas. The plane was on a training mission, with the intention of carrying out a simulated nuclear attack on San Francisco.

Its payload was a Mark IV nuclear bomb, weighing nearly five tonnes. While it had a lead core instead of plutonium, and was therefore unable to cause a nuclear explosion, it was still a real device loaded with explosives.

A Day That Shook The World: First nuclear submarine launched Show all 5 1 /5 A Day That Shook The World: First nuclear submarine launched A Day That Shook The World: First nuclear submarine launched 21st January 1954: The Nautilus, the world's first atomic submarine beginning her trials at Groton, Connecticut. Getty Images A Day That Shook The World: First nuclear submarine launched USS Nautilus, the world's first atomic powered submarine being launched at Groton in Connecticut. Getty Images A Day That Shook The World: First nuclear submarine launched Officers of the World's first nuclear powered vessel, the submarine USS Nautilus, stand to attention as Chief of Naval Operations Admiral Robert B Carney comes on board. Getty Images A Day That Shook The World: First nuclear submarine launched Admiral Robert B Carney observing the depth gauges of the world's first nuclear powered submarine 'Nautilus'. Getty Images A Day That Shook The World: First nuclear submarine launched A submariner puts a nickel in the jukebox on board the submarine USS Nautilus, the World's first nuclear powered vessel. The money will go toward the submarine's recreation fund. Getty Images

A 1998 interview with the co-pilot of the flight explained why this was done: “Without a real bomb the support systems could not be tested. There were some dummy bombs made of concrete that were used for load testing, but we weren't carrying one of those.

“This mission was to be as real as it gets short of war...The large amount of TNT in the bomb could have caused major damage where it would have impacted.”

The decision was made by the crew to drop the bomb into the Pacific Ocean before bailing out as they were unsure of how close they were to populated areas.

On Mr Smyrichinsky’s return to land, he researched the story of the downed B-36 and nuclear weapons of the time. In particular, he saw one photo of the ‘Fat Man’ bomb, a similar blimp type weapon, in several pieces before being assembled.

"It was a piece that looked very much like what I saw," he told the broadcaster. "The plane that was carrying the bomb, it crashed 50 miles south of where I found that object."

Mr Smyrichinsky contacted the Department of National Defence, who said the discovery had their “collective attention”.