The Broken Sub is probably the most infrequently dived of the four. It is the deepest, and it is also the closest to the Heads. It can therefore be uncomfortably close to the path taken by ships entering and leaving Port Phillip Bay. Boat operators must be aware of the shipping traffic during the dive period.
During the Broken Sub's scuttling, explosive charges caused the vessel to break in two sections. The break occurs just behind the conning tower, which tilts at a 45-degree angle. The wreck is in 39m and is surrounded by many schools of fish. These along with the extensive marine growth covering the hull, make this an interesting dive for photographers as well as wreck enthusiasts.
Being such a deep dive, we recommend that divers spend the last few minutes of their limited bottom time at a slightly shallower depth around the conning tower before beginning the final ascent. This area is usually inhabited by large numbers of fish, so there is plenty to look at before returning to the surface.
The Broken Sub is a marvelous venue for the experienced diver. Obviously more than one dive is required to fully explore it. With good visibility it is an outstanding dive.
Hazards and Precautions: The 39m depth calls for experience and training, correct equipment and very careful planning. Begin your ascent with plenty of air remaining for the inevitable decompression stops. Even at this depth surge can be a problem, especially when penetrating inside the wreck. If surge is present remain on the outside. Penetration into the wreck is possible, at the point where the ship has been broken, but the need for extreme caution cannot be overemphasized. In addition to the normal dangers involved in penetration diving at this depth, the Broken Submarine has the additional hazard of extensive jagged and twisted metal around the break. Once inside the wreck, it can become very dark, so good torches are essential. Care must be taken to avoid stirring up silt on the bottom, thus further reducing visibility.
Certification required: Deep 39m