The 250kg explosive, which was found on a Barwon Heads property earlier this month, has been handed to antique dealer Ian Royce.
Mr Royce said the bomb's discovery came as a big surprise.
"I couldn't believe what it was and how bizarre to find it in a backyard," he said.
"It's very unusual to find one now reasonably intact."
He managed to transfer it to his North Geelong antiques store on the back of his ute.
"I was so determined to get it on."
Mr Royce explained sea mines like the one found were chained to the bottom of the ocean during the war.
"They had little spines. If a ship even touched one of those mines it was full of TNT and would blow a hole in the side of any of those ships," he said.
After the war, many of the bombs were decommissioned and re-purposed as backyard incinerators.
"In those days, there was no green bin so you'd burn all your green rubbish in your backyard."
Mr Royce has listed the sea mine for sale for $1200, however the last one he sold went for $3000.