GRAND RAPIDS, Mich. (WOOD) — While fishing for treasure at the bottom of the Grand River, a group of local magnet fishermen’s unexpected catch prompted the Grand Rapids Bomb Squad to get involved.

Ryan McCollum said he was magnet fishing off the Sixth Street Bridge in Grand Rapids Saturday with his 8-year-old son Lochlan and cousin Chris Hample. That’s when Hample pulled up a 2-foot-long artillery shell.

It’s catches like this one that have the trio hooked on magnet fishing, calling themselves the Rustic Treasure Hunters.

McCollum said the concept is simple.

“Taking a high-powered magnet, hooking it to a rope and throwing it out into the water, and dragging it back and just seeing what you got,” he said.

It’s the mystery that keeps the Rustic Treasure Hunters coming back to the river every chance they get.

“You just never know what you’re going to catch,” McCollum said.

A group of magnet fishers at the Grand River find an artillery shell and notify authorities on April 17, 2021.

After a few hours of catching the usual nuts and bolts, McCollum said his cousin pulled up the unusual catch.

“I’m like, ‘What is that? There’s no way,’” McCollum said. “And then as I got closer, I saw it was an artillery shell, so that was very surprising for what you can find in the river.”

Unsure if the explosive could still be active, they called in the experts.

Once on scene, Grand Rapids police cleared the bridge for about an hour while the captain of the bomb squad took a closer look at their somewhat unusual find.

“It was as 75 millimeter armor piercing artillery shell, the bomb squad confirmed this too,” McCollum said. “It was actually used in Sherman tanks in WWII.”

A group of magnet fishers at the Grand River find an artillery shell and notify authorities on April 17, 2021.

How it ended up in the Grand River may forever be a mystery. McCollum said the bomb squad captain tossed around a few plausible theories.

“He thought someone (could’ve) brought it back from the war, so they had it and then thought I’ve got to get rid of this, so threw it in the river,” McCollum said.

Though the bomb squad captain deemed the shell safe enough to transport, the item remains in police custody, where it will be further analyzed and then destroyed.

They may not be able to keep the shell as a souvenir, but the Rustic Treasure Hunters will forever treasure the catch, posting the video of Saturday’s saga on social media.