HMAS J2 in 1920
|Builder:||HM Dockyard, Portsmouth|
|Launched:||6 November 1915|
|Fate:||Transferred to Australia, 25 March 1919|
|Acquired:||25 March 1919|
|Decommissioned:||12 July 1922|
|Fate:||Sunk 1 June 1926|
|Class and type:||British J class submarine|
|Length:||275 ft (84 m)|
|Beam:||22 ft (6.7 m)|
|Draught:||14 ft (4.3 m)|
|Range:||4,000 nmi (7,400 km; 4,600 mi) at 12 kn (22 km/h; 14 mph)|
|Test depth:||300 ft (91 m) max|
Design and construction
The J class was designed by the Royal Navy in response to reported German submarines with surface speeds over 18 knots (33 km/h; 21 mph). They had a displacement of 1,210 tons surfaced, and 1,820 tons submerged. Each submarine was 275 feet (84 m) in length overall, with a beam of 22 feet (6.7 m), and a draught of 14 feet (4.3 m). The propulsion system was built around three propeller shafts; the J-class were the only triple-screwed submarines ever built by the British. Propulsion came from three 12-cylinder diesel motors when on the surface, and electric motors when submerged. Top speed was 19 knots (35 km/h; 22 mph) on the surface (the fastest submarines in the world at the time of construction), and 9.5 knots (17.6 km/h; 10.9 mph) underwater. Range was 4,000 nautical miles (7,400 km; 4,600 mi) at 12 knots (22 km/h; 14 mph).
Armament consisted of six 18-inch torpedo tubes (four forward, one on each beam), plus a 4-inch deck gun.  Originally, the gun was mounted on a breastwork fitted forward of the conning tower, but the breastwork was later extended to the bow and merged into the hull for streamlining, and the gun was relocated to a platform fitted to the front of the conning tower.  44 personnel were aboard.
After the war, the British Admiralty decided that the best way to protect the Pacific region was with a force of submarines and cruisers. To this end, the offered the six surviving submarines of the J-class to the Royal Australian Navy as gifts. J1 and her sisters were commissioned into the RAN in April 1919, and sailed for Australia on 9 April, in the company of the cruisers Sydney and Brisbane, and the tender Platypus. The flotilla reached Thursday Island on 29 June, and Sydney on 10 July. Because of the submarines' condition after the long voyage, they were immediately taken out of service for refits.
Apart from local exercises and a 1921 visit to Tasmania, the submarines saw little use, and by June 1922, the cost of maintaining the boats and deteriorating economic conditions saw the six submarines decommissioned and marked for disposal.
The J2 wreck, also known as "39 Metre Sub", "130 Foot Sub", "Broken Sub" or "Deep Sub", is submerged in 39 metres (128 ft) of water. The wreck lies on its keel running North-South with its bow pointing out to sea. During its scuttling the bow section broke off, exposing the forward torpedoes tubes and bow modifications. The wreck is accessible by experienced divers, but it is the deepest and most difficult of the four J class submarine wrecks in the area.
- Bastock, Australia's Ships of War, p. 86
- "HMAS J2". Royal Australian Navy. Retrieved 2011-03-13.
- Victorian Ships' Graveyard Wrecks, retrieved 2011-03-13
- Dive Site - J2 Submarine, retrieved 2011-03-13
- Milowka, Agnes, Victoria's J Class Submarines, archived from the original on 2011-03-13
- Arnott, Terry, WWI J Class Subs, Maritime Archaeology Association Of Victoria, archived from the original on 2011-03-13
- Bastock, John (1975). Australia's Ships of War. Cremorne, NSW: Angus and Robertson. ISBN 0207129274. OCLC 2525523.