

The HMAS J4 is one of Australia's few diveable submarine wrecks, sitting upright on the seabed in Victoria's deeper coastal waters at 26 to 27 metres. The hull is well encrusted with kelp and seaweed, giving it a distinctly austere, overgrown character. Visibility ranges from 5 to 15 metres depending on conditions, and strong currents are a consistent feature here, demanding solid buoyancy control and careful dive planning. Surge compounds the challenge near the wreck itself, and entanglement risks from growth and structure mean penetration attempts are not appropriate. This is a boat-access site best suited to experienced wreck divers comfortable in variable, demanding conditions.
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Winter months from June through August typically offer the clearest water on this site, making them the preferred window despite the cold. Plan your dive around slack water where possible, as the current here can make working the wreck genuinely difficult.
The wreck is located in the ship graveyard off Port Phillip Heads. It is accessible via boat, with trips from Portsea taking approximately 20-25 minutes.
The wreck is very prone to strong surge, which can be dangerous and push divers into or against the wreck. Strong currents are common. Penetration is possible but hazardous due to tight spaces and potential for silt-out.
Depth
26-27m
Visibility
5-15m
Skill Level
Advanced
Entry
Boat
Boat required
Water Temp
13-23°C
Current
Strong
Typical Dive
35 min
Best Time
Jun, Jul, Aug
Yes, HMAS J4 Submarine in Melbourne is a boat-access-only dive site. You will need to book with a local dive operator or charter a boat to reach it.
HMAS J4 Submarine in Melbourne requires advanced diving skills. Expect deeper depths, currents, or challenging conditions that are not suitable for newly certified divers.
Diving at HMAS J4 Submarine in Melbourne requires the following certifications: Advanced. Always dive within your training limits.
A 7mm wetsuit or semi-dry is recommended for diving at HMAS J4 Submarine in Melbourne. Water temperatures range from 13°C to 23°C.
HMAS J4 Submarine in Melbourne is home to kelp and seaweed. Marine life sightings vary by season and conditions.
The best months to visit HMAS J4 Submarine in Melbourne are June, July, and August. Conditions outside these months can still be good but are less predictable.
HMAS J4 Submarine in Melbourne has depths ranging from 26 metres to 27 metres.
A typical dive at HMAS J4 Submarine in Melbourne lasts approximately 35 minutes. Actual dive time depends on depth, air consumption, and conditions.
HMAS J4 Submarine in Melbourne can have strong currents. Advanced experience with drift diving and current navigation is recommended.
Visibility at HMAS J4 Submarine in Melbourne typically ranges from 5 metres to 15 metres. Conditions vary with weather, tides, and seasons.