Australian Navy divers have discovered an explosive mystery lying at the entrance to Sydney harbor - four vintage bombs or shells that may be more than 100 years
The 3 ft. (1 m) long projectiles and bombs, thought to date from the 1870s to 1890s, were blown up to get rid of any danger.
How the munitions ended up 200 m offshore was unknown, Lt Commander Mike Gough said on Tuesday.
"I'm not able to speculate on that," Gough said.
The cliffs of North Head and South Head at the entrance to Sydney harbor were fortified around that time, when the British colony feared Tsarist Russia and American raids.
Guns were placed on South Head in 1871 after rumors circulated that an expedition of free-booters had sailed from San Francisco to ransack Sydney, according to military documents.
The ordinance was first discovered by recreational divers who told authorities they looked like World War II bombs.
Although at 72-78 ft. (22-24 m) under water they were not considered a hazard to shipping, the Navy decided to detonate them because of a potential risk to other recreational divers, said Fleet public affairs officer Andrew Herring.