The J-class were the fastest submarines in the world when they were laid down for the Royal Navy in 1915: 84 m long, 1,210 t surfaced and 1,820 t submerged, driven by three diesels for 19 knots on the surface. Six survivors of the class were gifted to the Royal Australian Navy in March 1919, sailed out with the depot ship HMAS Platypus, arrived in Sydney on 15 July 1919 and were based at Geelong from 1920. Post-war budget cuts saw them paid off at Western Port on 12 July 1922, and in January 1924 the Melbourne Salvage Company bought the flotilla for scrap.

J1 had launched at Portsmouth on 6 November 1915, commissioned on 15 March 1916 and served with the 11th Submarine Flotilla at Blyth on the North Sea. Stripped of engines and fittings at Williamstown, the hull was towed out through The Rip and scuttled on 26 May 1926. Today J1 is the deepest of the four Graveyard submarines and, for many Melbourne divers, the best.

She lies almost upright with a slight list to port on a flat sand and limestone bottom at 38 m, bow to the north-east, and the whole hull is intact from the fine, narrow bow to the stern hydroplanes. The conning tower rises to about 34 m and is the natural reference point; the pressure hull and casing are carpeted in bright yellow zoanthids that glow under a torch and give the boat its unmistakable Bass Strait look. Schools of butterfly perch, bullseyes and barber perch hang around the tower, and blue devilfish and crayfish live in the gaps between casing and pressure hull.

Penetration is possible: the open hatch beside the conning tower drops into the control room area, which is reasonably open and lit by the hatch, but the hull becomes pitch black towards the bow and the silt is fine and deep. Divers have died inside this submarine, and the local rule is simple – no line, no light, no entry. The exterior alone fills a 20-minute bottom time.

Because it sits at the edge of recreational limits with a meaningful transit through The Rip, J1 is dived less often than J4 and J5, usually as the deep dive on a two-tank charter on a calm day. It suits experienced deep divers and is a favourite first trimix or light-deco wreck for Melbourne technical trainees.

Boat only. Charters leave from Queenscliff Harbour (Red Boats, Dive Victoria Group) or Portsea Pier (Dive Victoria Group, Bayplay); drive Melbourne–Queenscliff via the Geelong Ring Road and Bellarine Highway (about 1 h 40 min) or Melbourne–Portsea down the Mornington Peninsula Freeway (about 1 h 45 min). Private boats launch at Queenscliff (Larkin Parade) or Sorrento ramps; the wreck lies a few kilometres outside The Rip, so time the run through the Heads for slack or a following tide.

Boat time from Queenscliff is roughly 20–30 minutes and from Portsea 30–40 minutes in a fast RIB, longer in a displacement charter boat. Gear is loaded at the harbour; there is parking at Queenscliff Harbour and along Point Nepean Road at Portsea.

Fully exposed Bass Strait. South-westerly swell is the killer: most charters will not run on a forecast over about 1.5 m, and anything from the south or west over 2 m makes the site undiveable and the passage through The Rip dangerous. Northerly and north-easterly winds flatten the sea; a calm morning after several settled days gives the best visibility (often 15–25 m in autumn and winter).

Surge is felt on the wreck in any swell over 1 m. Tidal streams outside The Heads are weaker than inside but still run; charters aim for slack water at Port Phillip Heads or a favourable tide for the transit. Winter westerlies close the site for weeks at a time.

The wreck sits in or near the shipping approach and pilot boarding ground, so a shot line, surface cover and a delayed SMB are mandatory.

Descend the shot to the conning tower (about 34 m) and orient yourself: bow lies north-east. Swim the deck forward along the port side to the bow torpedo tubes, cross over and return along the starboard side to the stern hydroplanes, then back to the shot for 20 minutes on the wreck. Trained divers may drop through the hatch beside the conning tower into the first, well-lit compartment.

Ascend the shot with stops from 9 m; most divers incur 5–15 minutes of deco.

Within recreational limits on air or EAN28–32 but an SMB, redundant gas (pony or twinset) and a computed deco plan are expected; many divers run it as a light-deco dive on nitrox with a 50% stage. Shot line descents and ascents only – free ascents in the shipping approach are not acceptable. Interior penetration requires a reel and primary/backup lights; the bow compartments silt out instantly.

Dive Victoria Group (Portsea and Queenscliff) – scheduled double-dive charters most weekends in season, weather permitting; Red Boats (Queenscliff) – regular weekend and weekday charters; Bay City Charters (Portsea/Queenscliff) and Chimney Rock Charters (Queenscliff) – regular weekend charters; Bayplay (Portsea) – occasional advanced charters. All treat the site as a deep/advanced dive and run it on the calmest days of the week.