The Royal Canadian Navy is sending a ship to investigate an object believed to be a lost Cold War-era “dummy” nuclear bomb jettisoned from a downed U.S. aircraft off the coast of British Columbia.

Commercial diver Sean Smyrichinsky spotted the mystery object about 80 kilometres south of Prince Rupert and reported it to the Canadian Armed Forces on Oct. 31.

Smyrichinsky said he was a riding a diving propulsion vehicle high above the rocky ocean floor when he spotted what looked like a large spherical rock below. As he got closer, he could tell the object was man made and far too big to have arrived on the small boats able to access the area.

“My first impression was, ‘What the heck is this,’ and a couple of seconds later when I got on top of it I thought, ‘Oh my, I found a UFO,’” he told CTVNews.ca.

The Department of National Defence says it’s likely a B4 weapon with a dummy lead capsule, carried by the U.S. Air Force B-36 aircraft that crashed in the area on Feb. 13, 1950.

Smyrichinsky, a 47-year-old veteran diver with 25 years’ experience, said it looks like a massive upside down cereal bowl with a hole punched in the centre.

“It didn’t look like it had been damaged in any type of explosion, that’s for sure. It’s perfectly round.”

He couldn’t hide his utter shock when he surfaced and returned to the boat. He described what he encountered, but nobody on board had the first idea what he was talking about.

“They said, ‘You’re crazy, you’re nuts,’” he recalls. The skipper handed him a marker and a napkin to sketch what he saw, but to no avail. The drawing sat on the boat until he could find more people with diving experience to show it to.

Getting in touch with fellow divers wasn’t a problem for Smyrichinsky, who owners a dive shop in Courtenay, B.C. He asked a few “old-timers,” but no leads surfaced.

Finally, after hearing about the story of the fallen B-36, he reached out to an old friend in the Canadian Forces, who is also an avid diver.

Historians with the Royal Aviation Museum of Western Canada say the bomber left an air base in Alaska to simulate a drop on San Francisco when ice build-up caused the plane to lose altitude. Three of its six engines burst into flames somewhere near the B.C. coast.

The 17-man crew was forced to bail out. The plane was set on autopilot and directed to crash into the Pacific. Five men did not survive.

The lost five-ton bomb was blimp-like in design, 3.25 meters long and 1.5 meters wide. The U.S. manufactured 550 units between 1949 and 1953.

Smyrichinsky’s story made the rounds in the military and he was told to contact a lieutenant colonel at CFB Esquimalt.

Naval officials aboard HMCS Yellowknife will investigate over the next several weeks. Smyrichinsky will guide the vessel to the site where a remote operated vehicle will collect photos and video of the object on the ocean floor.

“That particular capsule did not contain any nuclear material and there is not suspected radiological safety hazard from this ordnance,” DND spokesperson Ashley Lemire said in a statement to CTVNews.ca.

Smyrichinsky doesn’t want to say whether or not his find is indeed the so-called “Lost Nuke of 1950.” He puts the odds at “50/50.”