Vandals have damaged the wreck of a Japanese midget submarine in Sydney Harbour and made off with protected relics. The submarine, known as the M24, is a key piece of Australian World War II history and was one of three midget submarines that entered Sydney Harbour on May 31, 1942. It's believed divers entered the protected zone around the shipwreck and broke off and removed propeller blades and relics, reports The Sydney Morning Herald. One of the three submarines was blown up by its occupants after getting tangled in the boom net across the harbour. The M24 followed and fired torpedoes at the cruiser USS Chicago but instead hit the HMAS Kuttabul, killing 21 naval personnel. It then disappeared until 2006, when scuba divers discovered its wreck off a Sydney beach.