J4 Submarine Diving

This page is for the J4 wreck outside Port Phillip Heads, recorded separately in the national underwater heritage database. It is not J1, J2 or J5. The familiar Shallow and 90 Foot names describe this destination; “shallow” is a relative nickname among submarine wrecks, not a statement of easy conditions.

This is an offshore boat-dive destination. Confirm the intended wreck, departure arrangements and current operating requirements with the skipper or dive provider. A locality marker does not establish a usable mooring, vessel route or landing place.

The archived government dive sheet describes wreck sections on a rocky seabed, with the stern close to the reef and a detached bow exposing torpedo tubes. Its sketch identifies the conning tower and long hull. These are historical archaeological descriptions: deterioration can change the structure, and no recent inspection is claimed.

The government’s J4 discovery-trail page, updated in October 2011, places the submarine in 27.6 m of water. That figure describes the wreck’s water-depth setting. It does not supply separate measurements for the highest surviving structure, hull or deck. The names 26 Metre Sub and 90 Foot Sub are retained as aliases, without turning them into a surveyed range or a whole-dive maximum.

J4 entered Royal Navy service in July 1916. After the war it was one of six J-class boats transferred to Australia, commissioning into the Royal Australian Navy in March 1919. Following refitting in Sydney, J4 moved to the Geelong submarine base in 1920. High maintenance costs and economic pressures contributed to the class entering reserve in 1922. Sold for salvage in 1924, J4 sank at Williamstown wharf that July, was raised, and was sunk outside Port Phillip Heads in 1927. Salvage and subsequent deterioration explain why today’s visit is to a stripped wreck rather than an intact service submarine.

Offshore weather, swell, surge and boat recovery are relevant here. Current Weather describes atmospheric observations near the locality; it does not measure underwater visibility, currents or sea state. No tide timetable, drop time or current threshold is supplied.

Historic wreck protection and a designated no-entry protected zone are different things. Heritage Victoria’s current list of ten protected zones does not include this wreck. Its guidance requires a permit for entering a protected zone, and for recovering artefacts or disturbing a wreck. Leave structures and objects in place and check the current rules for the intended area.

Discuss the planned depth, offshore conditions and experience needed with the dive provider. A nickname or published depth does not establish suitability for an individual diver. Openings in a wreck do not imply a suitable entry route; this guide provides no penetration instructions. Review current marine notices before the trip.