The History Channel's "Bomb Hunters" has been following two crews from coast to coast as they search for ordnance dating as far back as World War I, Postmedia News reported.
The Quebec company, Mine/EOD, is run by former combat engineer Ray Tremblay. He told Postmedia with such old shells, it's too dangerous trying to defuse them, and they're destroyed in controlled detonations.
Such shells have been dubbed UXOs, for "unexploded explosive ordnance," the report said.
Military records indicate one of Canada's most heavily UXO-laced areas is Lac Saint-Pierre in Quebec, which was part of a military artillery training grounds.
About 300,000 shells were fired into the lake between 1952 and 2000 and a military rule of thumb is that one of every 25 shells fired didn't detonate.
Tremblay said the deep and swift waters are a challenge to divers searching for shells.
"It's a tricky place to work, with currents and waves," he said. "Visibility is zero, so you're dealing with munitions you can't see."
The first documentary episode airs Sunday.