Mulloka was an Australian-designed sonar system installed on ships of the Royal Australian Navy.[1] It was optimised for the warm and shallow waters common off Australia and used a high frequency.[2] The system was developed during the 1970s, with River-class destroyer escort HMAS Yarra being used as the trial ship for Mulloka between 1974 and 1979.[3] These trials ended on 17 August 1979 when the system was accepted for service.[4] Mulloka was subsequently fitted to all the RAN's River-class destroyer escorts and two of the six Adelaide-class frigates. It was removed from the frigates during the 2000s as part of an upgrade of their capabilities.[1]