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Miflex Inflator Hose | Purple

The Miflex Low Pressure (LP) BCD/Inflator/Jacket Purple colour hoses are supplied fitted with a standard Seatec style fitting, with an internal Schraider type valve and a 3/8" UNF male thread (to connect to the 1st stage regulator). There is a range of standard sizes to suit your requirements.

These hoses are suitable for the majority of BCD and Jacket connections, plus dry suit inflator connections, where a standard quick release coupler is utilised. But there are some fittings that require a different Quick Disconnect fitting. These we accommodate in our range with the use of adaptors that can be fitted to our regulator hoses (to convert them to an inflator hose).

J7 Submarine

Wreck Dive Wreck Dive | Shore access Shore access

Inside Port Phillip Wreck Dive Site

Fighting WWI Submarine to Marina Breakwater | Max Depth: 2 m (6.56 ft)

HMS J7 Submarine
HMS J7 Submarine
© Royal Australian Navy

The J7 Submarine at Sandringham Yacht Club is a unique visible feature of the marina, and is historically significant as one of the Royal Australian Navy's earliest submarines, predated only by the AE-1 and AE-2.

The J-7 differed from the other J-class submarines. The J7's submerged displacement of 1,760 tons was 60 tons less than that of her sister boats. The control room was repositioned further aft by circa 60 ft (18 m), between the main engine rooms. The conning tower moved with it. The 3-inch HA gun was mounted in a lower position at the forward end of the superstructure.

J7 Submarine History

Originally HMS J7, later HMAS J7, this is one of the seven J class submarines designed and built during WW1 by the British Royal Navy. The J class of submarines was a seven submarine class developed in response to claims that Germany was developing submarines that were fast enough (22 knots) to operate alongside surface fleets. The rumours were actually false.

The J Class design brief was for a submarine to operate on the wings of battle fleets, diving at the commencement of engagements, and picking off stragglers, damaged ships, and acting as an anti-submarine submarine.

This class of submarines were the only design of submarines ever to have had 3 screw propellers, and at the time were the fastest subs around with a surface speed of 19 knots (35 kpm). Six J class submarines were completed during mid-1916, while a seventh entered service in 1917.

HMS J7 commissioned in the Royal Navy on 15 September 1917 under the command of Lieutenant Commander F.H.D. Byron RN and was allocated to a flotilla based at Blyth, Northumberland. The wartime complement was 5 officers and 40 sailors.

HMS J7 Submarine Operations

J Class Submarine Control Room
J Class Submarine Control Room
Source: Royal Navy

On 5 November 1917 J7 departed Blyth for her first patrol. While on patrol in the North Sea on 6 March 1918 an enemy submarine was sighted, but J7 was unable to attack and the enemy passed from sight.

The submarine was under refit during April and May 1918 at Walker Naval Yard on the River Tyne. She sailed for patrol on 25 May and evaded a U-boat attack the same day.

On 10 July an enemy submarine was sighted and both vessels dived. Shortly after a sighting was made of an enemy submarine on the surface, going away, J7 surfaced, challenged and opened fire. The enemy dived. An enemy submarine was sighted on 23 July, but J7 was unable to attack and the enemy disappeared.

On 5 October 1918 J7 dived to intercept a reported submarine but broke off the search without contact.

The boat was at sea when the Armistice was signed on 11 November 1918. She returned to Blyth on 15 November. On 19 February 1919 she proceeded to Jarrow.

Although larger and more powerful than previous British submarines, the J class could not keep up with surface vessels and operated independently during the war. Between them, the submarines sank a U-boat, and heavily damaged two battleships. The J6 Submarine had been sunk in error in 1918 by a British ship.

HMAS J7 Submarine Operations

HMS J7 Submarine in 1919
HMS J7 Submarine in 1919
© Royal Australian Navy

Following the conclusion of hostilities in World War I, the Admiralty in 1918 presented the six remaining boats of the J Class to the Australian Government. All the submarines commissioned into the Royal Australian Navy at Portsmouth on 25 March 1919, as tenders to the submarine depot ship HMAS Platypus, J7 being the senior boat, under the command of Lieutenant Commander Oswald E Hallifax DSO, R.

The beam tubes were removed from all six J Class submarines before they sailed for Australia. The tubes were despatched separately to Garden Island. The reasons given for the removal were that the beam tubes were not a success and that increased accommodation was required.

On 9 April 1919 HMAS Platypus and the submarines, escorted by the light cruiser HMAS Sydney, sailed from Portsmouth for Australia, their first two ports of call being Gibraltar and Valetta. Other ports of call included Port Said, Aden, Colombo, Singapore, Thursday Island, and Brisbane. When they arrived in Australia on 15 July 1919, the six submarines were all in poor condition. They were taken in hand at Garden Island Dockyard for refitting. The last one to finish being refitted was the J7 submarine in June 1922.

After her refit was completed J7 sailed for the submarine base at Geelong, Victoria. The ironclad Cerberus was renamed HMAS Platypus II on 1 April 1921 and acted as a depot ship to the J Class submarines whilst stationed at Geelong. The HMAS Platypus II is not to be confused with the HMAS Platypus which was one of the six gift vessels which escorted the J submarines from England to Australia.

After uneventful service, little of which was spent at sea, J7 and her five sisters were paid off into Reserve at Western Port on 12 July 1922.

The decision to scrap the J7 submarine came on 16 January 1924 even though it was in fairly good condition after just being refitted. It was described as the last survivor of an obsolete class. She stayed in service for the longest period providing electricity for the Flinders Naval Depot. (The J3 also served this purpose prior to scuttling.)

J7 Submarine Details

Inside a J-class Submarine
Inside a J-class Submarine
© Royal Australian Navy

The J class Submarine Number 7 was built in 1916/1917 at Devonport Dee, United Kingdom, and launched on 12 February 1917. At that time the J class were the fastest subs in existence. Number 7 was the last J-class submarine to be built.

It's commonly believed that the J-class submarines were identical in dimensions and layout, but this is not so. Royal Navy drawings placed the J class into two groups of J1–4 and J5–7, and that the bridge of J7 was moved 60 feet aft compared to J5–6. Plans show a difference in overall length between the two groups, with J5–7 at 274 feet 9 inches being 9 inches shorter than J1–4 which were 275 feet 6 inches.

The overall length of the J7 Submarine was approximately 274.75 ft (84 m), beam 23.5 ft (7.16 m) and draught 14 ft (4.27 m) giving a displacement weight of 1,210 t (1,334 s-ton) surfaced and 1,760 t (1,940 s-ton) submerged.

The J-class submarines were powered by three 12-cylinder Vickers solid, direct reversing, 4-cycle, diesel engines of 14.5-inch bore and 14-inch stroke, producing a total of 3,600 HP at 380 rpm. For submerged running there were two Mather & Platt 700 HP electric motors, for a total of 1,400 HP, powered by four banks of 58 cell batteries.

The vessel had a maximum speed of 19 knots (35 kpm) surfaced and 9.4 knots (17 kpm) submerged, with a range of 4,000 nm (7,408 km) at 12 knots (22 kpm) and 2,250 nm (4,167 km) at full speed surfaced. The maximum safe diving depth was 300 ft (91 m). They J-class submarines were equipped with a powerful long-range wireless and were ideally suited to reconnoitre in enemy water.

J7 Submarine Conning Tower and Gun
J7 Submarine Conning Tower and Gun
© Royal Australian Navy

The J Class submarines principal weapons originally were:

  1. 6 x 18-inch (457 mm) torpedo tubes (4 bow, 2 beam)
  2. 1 x 4-inch (102 mm) gun
  3. The J1, for a brief period, was fitted with Depth charges

J7 Submarine Scuttling

J7 Submarine at Sandringham Yacht Club
J7 Submarine at Sandringham Yacht Club
© Peter Campbell

The J7 Submarine was towed from Cowes, where she had been lying at anchor, to Melbourne by the tug Minah to Footscray. The J7 was sold to Morris and Watts Machinery Merchant in October 1929, who after dismantling the J7 sold it to the Ports and Harbors Department Melbourne. The J7 Submarine was eventually scuttled on 6 August 1930 as a breakwater at Sandringham Yacht Club.

Four subs, J1, J2, J4, and J5, were scuttled in the Victorian Ships' Graveyard. Two were scuttled as breakwaters: J3 near Swan Island, and J7 at Sandringham Yacht Club.

See also, Heritage Council Victoria: J-7 Submarine,
Australian National Shipwreck Database: J-7 Submarine,
Royal Australian Navy: HMAS J7,
Sandringham Yacht Club: J7 Submarine,
Wikipedia: HMS J7, and
Wikipedia: J-class submarine.

Heritage Warning: Any shipwreck or shipwreck relic that is 75 years or older is protected by legislation. Other items of maritime heritage 75 years or older are also protected by legislation. Activities such as digging for bottles, coins or other artefacts that involve the disturbance of archaeological sites may be in breach of the legislation, and penalties may apply. The legislation requires the mandatory reporting to Heritage Victoria as soon as practicable of any archaeological site that is identified. See Maritime heritage. Anyone with information about looting or stolen artefacts should call Heritage Victoria on (03) 7022 6390, or send an email to

Boon Wurrung / Bunurong country
Boon Wurrung / Bunurong country

Traditional Owners — This dive site is in the traditional Country of the Boon Wurrung / Bunurong people of the Kulin Nation. This truly ancient Country includes parts of Port Phillip, from the Werribee River in the north-west, down to Wilson's Promontory in the south-east, including the Mornington Peninsula, French Island and Phillip Island, plus Western Port. We wish to acknowledge the Boon Wurrung as Traditional Owners. We pay respect to their Ancestors and their Elders, past, present and emerging. We acknowledge Bunjil the Creator Spirit of this beautiful land, who travels as an eagle, and Waarn, who protects the waterways and travels as a crow, and thank them for continuing to watch over this Country today and beyond.


J7 Submarine Location Map

Latitude: 37° 56.599′ S   (37.943317° S / 37° 56′ 35.94″ S)
Longitude: 144° 59.680′ E   (144.994667° E / 144° 59′ 40.8″ E)

Datum: WGS84 | Google Map | Get directions
Added: 2012-07-22 09:00:00 GMT, Last updated: 2022-04-26 01:04:06 GMT
Source: GPS
Nearest Neighbour: Sandringham Pier Breakwater, 155 m, bearing 185°, S
J-Class Submarine, 1760 ton.
Built: Devonport Dee, United Kingdom, 1916.
Scuttled: 6 August 1930.
Sandringham, Bayside, Port Phillip.
Depth: 2 m.

DISCLAIMER: No claim is made by The Scuba Doctor as to the accuracy of the dive site coordinates listed here. Should anyone decide to use these GPS marks to locate and dive on a site, they do so entirely at their own risk. Always verify against other sources.

The marks come from numerous sources including commercial operators, independent dive clubs, reference works, and active divers. Some are known to be accurate, while others may not be. Some GPS marks may even have come from maps using the AGD66 datum, and thus may need be converted to the WGS84 datum. To distinguish between the possible accuracy of the dive site marks, we've tried to give each mark a source of GPS, Google Earth, or unknown.


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