River - class destroyer escort The River class was a class of six destroyer escorts ( originally designated anti - submarine frigates ) operated by the Royal Australian Navy ( RAN ) . Plans to acquire four vessels , based on the British Type 12M ( or " Rothesay " class ) frigate , began in the 1950s . The first two vessels had some slight modifications to the design , while the next two underwent further changes . Two more ships were ordered in 1964 , following the Melbourne - Voyager collision ; these were based on the Type 12I ( or " Leander " class ) frigate . By the 1990s , all six ships had left service . Two were sunk as part of tests , and a third was scutted as an artificial reef , while the other three ships were scrapped . Design and construction . In August 1950 , the Australian government announced plans to acquire a new class of anti - submarine warfare frigates , based on the British Type 12M ( or " Rothesay " class ) frigate design . Originally six were planned , with construction to be split between Cockatoo Island Dockyard in Sydney and Williamstown Naval Dockyard in Melbourne , but only four were approved . The first two ships , and , were based directly on the " Rothesay " class , with changes to fire control system , air warning radar , and habitability to meet RAN operating conditions . The second pair , and , were modified to carry a variable - depth sonar over the stern . Although originally classified as frigates , the ships ' designation was later changed to destroyer escort . In 1964 , the aircraft carrier collided with the destroyer , resulting in the destroyer ' s sinking . In order to replace the lost capability , the Australian government ordered another two River class ships , and . Unlike the previous four , the new ships were based on the more advanced Type 12I ( or " Leander " class ) design . The ships had a displacement of 2 , 150 tons at standard load and 2 , 700 tons at full load . They were 370 ft . ( 113m ) long , had a beam of 41 ft . ( 12 . 5m ) , and a draught of 13 ft . ( 3 . 9 m ) . Propulsion was provided by two double - reduction gearded turbines , which supplied to two propeller shafts , allowing the vessels to reach . Maximum range was at . The ship ' s company consisted of 250 personnel . Weapons fit for the first four ships at commissioning consisted of two 4 . 5 inch Mark 6 guns in a single twin turret , two 40 mm Bofors s in a twin mount , and two Limbo anti - submarine mortars . During the 1960s , a quadruple Sea Cat anti - aircraft missile launcher was fitted in place of the Bofors , and one of the Limbo mortars was removed in favour of an Ikara missile launcher . " Stuart " was the first RAN ship fitted with Ikara , and " Derwent " the first to carry Sea Cat . In the early 1990s , the missile systems were removed from all active Rivers , with an Army RBS 70 unit available for use if required . Operational history . During their careers , the River class ships spent most of their time in Australian waters or on multinational exercises , but were regularly deployed to the Far East Strategic Reserve , and saw service during the Indonesia - Malaysia Confrontation . During 1967 and 1968 , " Stuart " and " Yarra " were used to escort the troop transport on voyages to Vietnam . During the mid - 1970s , " Yarra " underwent a half - life refit , which included the removal of her remaining Limbo , and installation of a Mulloka sonar . " Parramatta " underwent a more extensive modernisation during the late 1970s , with a new fire control system , modification of the boilers and electrical system , and habitability improvements . " Stuart " and " Derwent " underwent similar modernisations between 1979 and 1985 . Modernisation was planned for " Swan " and " Torrens " during the mid - 1980s , but a lack of funding meant that the ships only underwent a half - life refit . At the start of 1984 , " Stuart " became the first RAN vessel permanently assigned to , the new base in Western Australia . In 1992 , reports of sexual harassment aboard " Swan " prompted investigations by the Australian Defence Force and a Senate committee review . Decommissioning and fate . " Yarra " was decommissioned on 22 November 1985 . There were plans to keep her in service as a training vessel , but the decision was to keep active in this role , and " Yarra " was placed in reserve . The other ships of the class were decommissioned during the 1990s . " Derwent " was sunk during explosives testing in 1994 . " Swan " was scuttled as an artificial reef in 1997 . " Torrens " was torpedoed by the " Collins " class submarine during a weapons test in 1999 . The other three ships were broken up for scrap . Specifications . Note : although these ships are grouped together as a single class , there were many significant differences between the first two units , second two units ( Type 12M ) and the final two units ( Type 12I ) .