When a British man found an object that had washed up ashore, he decided to use it in a game of fetch with his dog - but that could have been deadly, since he discovered it was a dangerous piece of history, according to UK's The Independent.

The mysterious object washed ashore on a beach in Essex, according to Essex police. But what was the mysterious object?

According to an off-duty explosives expert who was at the beach, the object the beach-goer was throwing to his dog was actually a live grenade believed to be from World War II.

The bomb expert stopped the game of fetch and set up a 30-yard boundary around the grenade, according to The Independent. Police and coastguards were then notified.

The grenade, the fifth one found in the area in weeks, was removed by Explosive Ordinance Disposal officers (EOD).

The other grenades were all detonated by EOD officers and police have an idea of where they are coming from.

"It would appear that the grenades might have been in a crate that ended up in the sea during the Second World War," said Inspector Paul Butcher.

"That crate might be breaking up or has been disturbed by dredging in the port and has resulted in these five devices being washed ashore along the same stretch of beach," Butcher told The Independent.

There are, however, conflicting reports saying that the beach-goer who found the grenade was actually a woman walking her dog and the game of fetch never happened.

Clair Watson, 41, told UK's Mirror, "I joked to the policeman I had been about to throw it for the dog but I would never have thrown it."

According to the Mirror, the person that helped identify the grenade wasn't an off-duty explosives expert, but rather a person who called his army explosives expert son.

Regardless, Butcher is advising beach-goers to be careful while on the beach and to "dial 999" if they find any grenades.

"Anyone who finds a grenade should not touch it or move it but should call police immediately," Butch told The Independent.

Keep checking back for more updates.