She displaced 768 tons; she was 178 feet 9 inches long, had a beam of 32 feet 3 inches and a draft of 11 feet 3 inches. She could achieve a speed of 11.5 knots; and had a crew of 32.
She was armed with one 12 pounder 12 cwt in High Angle Mk IV mounting on aft boat deck, one .303 Lewis machine gun, one .303 Vickers machine gun and two .30 inch Marlin machine guns.
Koala sailed for Darwin on 9 April 1940, arriving there on 29 April. Following the first air raid on Darwin on 19 February 1942, she was transferred to Brisbane for some three months before returning to Darwin on 5 June 1942 where she resumed her boom defence duties, serving in that capacity until 30 April 1945.
In the post war period Koala served in eastern and western Australian waters and in New Guinea where she was involved in harbour duties, buoy laying and recovery and boom defence training.
Her sea-going service ended at Sydney on 8 November 1956 having steamed 79,183.9 nautical miles. On 18 April 1957 she was placed in Reserve Commission at Waverton Boom Depot.
She received the battle honour "Darwin 1942–43".
Koala was eventually sold late in 1969 and was then used as a gravel barge in Brisbane. On 28 January 1974, during the disastrous Brisbane flood, the she severely damaged the Centenary Bridge at Jindalee when she broke free of her moorings.
she was subsequently sunk using explosives where it came to rest. Later, in 1976, consideration was given to raising the vessel but it is not known whether these efforts were successful.