ESSEX COUNTY (PIX11) – The Passaic River, which runs through seven counties across northern New Jersey is not only chock full of history, but plenty of buried treasure.

“You’d be surprised by the stuff you can catch out here,” magnet fisherman Robert Szalai said.

That was certainly the case this past weekend, when a fellow magnet fisherman pulled what authorities described as an “unexploded military shell” out from the bottom of the river. The discovery, which happened near the Lyndhurst Bridge in Nutley on Saturday afternoon, prompted a massive police response, including the bomb squad with the Essex County Sheriff’s Department.

The military shell, which officials say was live, was secured and removed to an undisclosed location where it was detonated.

The fisherman who pulled it out, Kevin Obiedzinski, later shared the big find on Instagram. He was praised by law enforcement for his “quick thinking.”

While it remains unclear how this military shell even ended up in the waters of the Passaic River, the  fishermen who make these discoveries have their own theories.

“Maybe someone did not know what they had and they wanted to dispose of it without throwing it into the garbage and hurting anybody,” Szalai explained.

Knives, jewelry and even firearms have all been discarded in the river and later pulled out by magnet fishermen, Szalai said.

The practice of magnet fishing involves using a strong magnet to remove large debris from bodies of water — a trend that exploded in popularity at the height of COVID. The area near the Lyndhurst Bridge is a hotbed for dumping and scavengers, Szalai said.

“Every time this floods, this becomes a new spot because it flushes everything down and you could start all over again,” Szalai, who has been a magnet fisherman for a little over a year, told PIX11 news.

The growing community of magnet fishermen are making discoveries every day. According to Szalai, who even launched a YouTube page about all his unique finds, it’s a matter of being smart about what you find.

“When in doubt, call the cops,” he said.