Castle Rock is a reef and pinnacle site located off Portsea, Australia. The topography features a wall and reef structure at depths between 12 and 20 metres. This site is defined by strong tidal currents flowing through Port Phillip Heads, necessitating dives timed strictly for slack water. Visibility typically ranges from 5 to 15 metres. Due to the challenging currents and potential for significant swell, this site is suitable only for advanced divers. Water temperatures fluctuate between 13C and 19C, making a 7mm wetsuit or drysuit essential. Boat access is required for all dives, which generally last around 45 minutes.

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.

Catch Bag Reef is a boat-accessible site located in Portsea, Australia, featuring depths between 16 and 18 metres. This reef is a drift dive site, which must be conducted on the flood tide due to moderate to strong currents. Visibility ranges from 10 to 30 metres. Divers frequently encounter Western Blue Devil, wrasses, and sea stars. Other species recorded at the site include Port Jackson Shark, Southern Rock Lobster, Fiddler Ray, and various nudibranchs. Given the current, this site is suitable for intermediate divers who should plan their entry and exit to align with the water flow.

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.

Boarfish Reef in Portsea is a drift dive site characterised by strong currents ranging from 1 to 4 knots. Divers explore the reef structure at depths between 10 and 22 metres, with an average depth of 16 metres. Due to the significant currents and proximity to the hazardous Port Phillip Heads area, this site is suited for intermediate divers with drift experience. Visibility typically fluctuates between 10 and 25 metres. Boat access is required, and divers must remain vigilant regarding heavy boat traffic and large ships in the vicinity. The use of a surface marker buoy is essential for safe ascents.

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.

Lonsdale Wall is a vertical reef and cave system located at the entrance to Port Phillip Bay. The wall drops from 12 to 45 metres, with an average depth of 25 metres. Due to its position in a high-velocity tidal zone, this site is strictly for advanced divers and requires boat access. Dives must be timed precisely for slack water to manage strong currents, and the site is often dived as a drift. Divers should be prepared for deep diving conditions, potential decompression requirements, and active shipping traffic. Visibility typically ranges from 5 to 15 metres, and water temperatures fluctuate between 13C and 18C throughout the year.

Flat Rock is a reef site located near Port Phillip Heads, offering depths between 12 and 25 metres. The topography features a mix of reef sections, caves, and overhangs, which require awareness of the overhead environment. Due to its proximity to the heads, the site is subject to moderate to strong tidal currents and surge; diving must be timed for slack water. Visibility is highly variable, ranging from 1 to 20 metres. Access is by boat only, and guided tours are available for those unfamiliar with the local conditions. The water temperature ranges from 13C to 18C, necessitating appropriate thermal protection.