Wikipedia - History of the Royal Australian Navy...(excerpts)
The Royal Australian Navy has seen action in every ocean of the world. The RAN first saw action in World War I, and distinguished itself in three oceans.

At the outbreak of war, the RAN stood at 3,800 personnel and consisted of sixteen ships, including the battlecruiser Australia, the light cruisers Sydney and Melbourne, the destroyers Parramatta, Yarra, and Warrego, and the submarines AE1 and AE2. The light cruiser Brisbane and three destroyers were under construction, and a small fleet of auxiliary ships was also being maintained. As a consequence the Royal Australian Navy at the start of the war was a small but formidable force.[16]


The Australian squadron entering Simpson Harbour, Rabaul, September 1914
Australian ships first saw action Asian and Pacific theatre; assisting in the attack on German New Guinea by the Australian Naval and Military Expeditionary Force (AN&MEF). Germany had colonised the northeastern part of New Guinea and several nearby island groups in 1884, and the colony was currently used as a wireless radio base, Britain required the wireless installations to be destroyed because they were used by the German East Asia Squadron which threatened merchant shipping in the region. The objectives of the force were the German stations at Yap in the Caroline Islands, Nauru, and Rabaul in New Britain. On 30 August 1914, the AN&MEF left Sydney under the protection of Australia and Melbourne for Port Moresby, where the force met the Queensland contingent, aboard the transport HMAHS Kanowna. The force then sailed for German New Guinea on 7 September, leaving Kanowna behind when her stokers refused to work. Sydney and her escorting destroyers met the AN&MEF off the eastern tip of New Guinea. Melbourne was detached to destroy the wireless station on Nauru, while on 14 September, Encounter bombarded a ridge near Rabaul,[17] while half a battalion advanced towards the town. The only major loss of the campaign was the disappearance of the submarine AE1 during a patrol off Rabaul on 14 September 1914.[18][19]
On 9 November 1914, the German light cruiser SMS Emden attacked the Allied radio and telegraph station at Direction Island in the Cocos (Keeling) Islands. The inhabitants of the island managed to transmit a distress signal, which was received by Sydney, only 50 miles (80 km) away. Sydney arrived within two hours, and was engaged by Emden. Sydney was the larger, faster and better armed of the two, and eventually overpowered Emden, with captain Karl von Müller running the ship aground on North Keeling Island at 11:15 am. At first, Emden refused to strike its colours and surrender; Sydney fired on the stationary Emden until it eventually struck its colours. The Battle of Cocos was the first battle the RAN participated in.[11]


HMAS Pioneer off East Africa in 1916
On 6 February 1915, the obsolescent light cruiser HMAS Pioneer joined the East African campaign. On 6 July, she engaged the German cruiser SMS Königsberg and German shore batteries, during the Battle of Rufiji Delta. Pioneer remained off East Africa and took part in many bombardments of German East Africa, including Dar-es-Salaam on 13 June 1916. Pioneer then returned to Australia, to be decommissioned in October 1916.
During the Naval operations in the Dardanelles Campaign the Australian submarine AE2 became the first Allied warship to breach the Turkish defences of the Dardanelles. AE2 spent five days in the area, was unsuccessfully attacked several times, but was unable to find any large enemy troop transports. On 29 April 1915, she was damaged in an attack by the Turkish torpedo-boat Sultan Hisar in Artaki Bay and was scuttled by her crew. The wreck of AE2 remained undiscovered until June 1998.[20]
Ships of the Royal Australian Navy also assisted the Royal Navy in the blockade of the German High Seas Fleet. In February 1915, HMAS Australia joined the British Grand Fleet, and was made flagship of the 2nd Battle Cruiser Squadron.[21] Australia was not involved in the Battle of Jutland; in April, the battlecruiser was damaged in a collision with sister ship HMS New Zealand, and she did not return to service until June.[21][22] Three RAN ships were present during the surrender of the German High Seas Fleet; Australia, Sydney, and Melbourne, with Australia leading the port division of the Grand Fleet as it sailed out to meet the Germans.[23][24]
The most decorated Australian Naval unit of World War One, however was not a ship at all, but the Royal Australian Navy Bridging Train,[25] a land-based unit composed mostly of reservists which landed at Suvla Bay with the British IX Corps and was responsible for receiving, storing and distributing the supplies, including potable water, of the British troops at Suvla.[26] Due to their position working the piers and landings at Suvla, the Train was the last Australian unit to depart the Gallipoli Peninsula.[27] After Gallipoli, the Train was sent to the Middle East, where they made a second amphibious landing at the Battle of Magdhaba, before returning to Australia and being disbanded after a series of miscommunications during May 1917.[28]
Expansion during the war had been limited, with the RAN growing to include thirty-seven ships and more than 5,000 personnel by 1918.[29] The RAN's losses had also been modest, only losing the two submarines AE1 and AE2, whilst casualties included 171 fatalities – 108 Australians and 63 officers and men on loan from the Royal Navy, with less than a third the result of enemy action.[30]