The HMAS J5 is a submarine wreck resting upright on the seabed at depths between 30 and 36 metres. This advanced dive requires boat access and is subject to moderate currents of 1 to 2 knots, which can funnel through the structure. Visibility typically ranges from 5 to 10 metres. The wreck features an overhead environment with tight internal spaces, making penetration hazardous due to potential silt-out and structural deterioration. Divers should be prepared for water temperatures between 13C and 18C. Given the depth and conditions, redundant air sources and multiple lights are mandatory for those planning to explore the interior of the hull.

The Rotomahana wreck is a deep, advanced dive located off Portsea, Australia. The site features a wreck structure and an adjacent wall at depths between 30 and 40 metres, with an average depth of 38 metres. Due to its proximity to Port Phillip Heads, the area experiences powerful tidal currents, making slack water the only safe time to dive. Visibility typically ranges from 10 to 30 metres. Given the depth and potential for strong currents, this site is strictly for experienced divers. A 7mm wetsuit with hood and gloves or a drysuit is recommended to manage water temperatures ranging from 13 to 18C.

The SS Coogee is a wreck dive situated in the treacherous entrance to Port Phillip Bay known as The Rip. Resting at depths between 29 and 35 metres, this site is strictly for advanced divers due to extreme tidal currents that can exceed 6 knots. Diving must be conducted exclusively during slack water to ensure safety. Visibility ranges from 4 to 25 metres, with the best conditions typically occurring during the winter months. Access is by boat only, located 4 kilometres from shore. Given the depth and the potential for strong currents, divers should plan for decompression and use a local charter operator familiar with the specific tidal windows.

The HMAS J4 is an upright submarine wreck resting at a depth of 26 to 27 metres off Portsea. This boat-access site is suited for advanced divers due to frequent strong currents and surge. The hull is heavily encrusted with kelp and seaweed. Visibility typically ranges between 5 and 15 metres. Due to the risk of entanglement and potential for silt-out, penetration is hazardous. Divers should plan their visit around slack water to manage the challenging conditions. Species recorded around this area include weedy seadragons, giant cuttlefish, western blue devils, and various wrasse species.

The HMAS Canberra is a decommissioned warship resting upright on a sandy bottom near Portsea. The wreck offers a range of depths from 12 metres at the superstructure to 33 metres at the hull, requiring advanced buoyancy and gas management skills. Divers access the site by boat, and the wreck features multiple entry and exit points for penetration. Conditions vary, with moderate currents and surge common; the site is best dived during slack tide in calm weather. Visibility typically ranges between 6 and 15 metres. Due to water temperatures between 13C and 18C, a 7mm wetsuit or drysuit is recommended for the average 40-minute dive.

The HMAS J2 is a decommissioned Royal Australian Navy submarine resting upright on the seafloor at depths between 37 and 39 metres. Located 3000 metres offshore, this wreck is a deep dive site requiring boat access. The hull is broken in two places, with a collapsed section behind the conning tower. Due to the risk of fine silting and disorientation, penetration is not recommended. Divers should be prepared for cold water temperatures, potential low visibility, and boat traffic as the site lies within a shipping lane. This site is suitable for advanced divers with wreck experience who can manage decompression requirements and overhead environments.

The SS Courier is an advanced wreck dive located off Portsea, resting upright on a sandy bottom at depths between 40 and 42 metres. Situated near the entrance to Port Phillip Bay, the site is subject to strong tidal currents and requires careful planning around slack water. Visibility is highly variable, ranging from 5 to 35 metres. The wreck features an overhead environment with potential for penetration and entanglement. Due to the depth and current, this site is strictly for experienced divers who are well-equipped for decompression diving. Boat access is required to reach the site, and divers must remain vigilant regarding boat traffic and nitrogen narcosis.

Dragon's Lair is a boat-access reef dive located off Portsea, Australia. Divers typically explore depths between 12 and 18 metres, with an average depth of 15 metres. The site is suited for intermediate divers due to moderate currents and visibility ranging from 5 to 10 metres. Surge can be present, requiring caution during boat entry and exit. Tidal flow significantly influences conditions, making precise timing essential for a manageable dive. Species recorded around this area include Weedy Seadragons, Pot-bellied Seahorses, Western Blue Devils, and various wrasses. Divers should maintain close contact with their buddy and monitor changing conditions throughout the dive.