Operators of a British fishing trawler were surprised by what they found in their nets last week — a German mine that was at least 80 years old.

Popular Mechanics reported that Royal Navy divers lowered the mine back into the water after a brief investigation, and then blew it up, sending a spout of water into the sky.

Lieutenant Commander Mark Shaw, Commanding Officer of the Royal Navy’s Northern Diving Group, told the BBC that the submarine-laid mine was in “remarkable” condition considering it had been in the water for 80 years.

The fishing trawler, assigned to Scotland’s fisheries management agency, discovered the mine; the Scottish government said the marine research ship had quickly alerted the emergency services and other agencies once the mine had been discovered.

According to Maritime Executive, Royal Navy divers receive about one request a day for assistance across the U.K., including requests for help with “historic ordnance.” Unexploded bombs and other ordnance left over from World War I and World War II are an ongoing problem across Europe.

This tweet by the Royal Navy features footage of the detonation.