Lonsdale Arches is a boat-access reef and cave system located in Port Phillip Heads. The site features arches and cave structures at depths ranging from 10 to 18 metres, with an average depth of 14 metres. Visibility typically spans 10 to 15 metres. This site is exposed to strong tidal currents from Port Phillip Heads, making it essential to dive only during slack water to avoid being swept away. Due to the proximity of the shipping channel, boat traffic is a constant consideration. Water temperatures range from 13C to 19C, necessitating a 7mm wetsuit or drysuit. The site is suitable for intermediate divers.

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.

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 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 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 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.

Lonsdale Reef is a complex site featuring a combination of reef, wall, pinnacle, and wreck topography. Located in the entrance to Port Phillip Bay, the site is subject to extremely strong tidal currents. Diving is restricted to the short slack water window, which can last as little as 30 minutes. Depths range from 10 to 45 metres, with an average of 16 metres. Visibility varies between 10 and 30 metres. Due to the challenging currents, heavy boat traffic, and potential for surge, this site is suitable for intermediate to advanced divers. Access is available by both shore and boat, with the site situated 1000 metres from the shore.

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.