HMAS Koompartoo was a Royal Australian Navy (RAN) auxiliary boom defence vessel, and former Sydney harbour ferry.Built in 1922 by the Walsh Island Dockyard and Engineering Works in Newcastle, New South Wales.Koompartoo was constructed with 18 watertight compartments, regarded as being unsinkable and therefore was not required to carry lifebelts.After service with Sydney Ferries, she was purchased by the British Ministry of War Transport for service in the Middle East and began conversion work at Mort's Dock, Sydney.