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.

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.

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.

The Grotto in Portsea is a reef, wall, and cave dive site ranging from 12 to 25 metres in depth. Due to its proximity to the Port Phillip Heads, the site is subject to strong tidal currents and must be dived at slack water. Divers encounter a variety of marine life, including very common Western Blue Devil, common Blue Throated Wrasse, wrasses, sea stars, and Old Wife. Uncommon species recorded here include Giant Cuttlefish, Fiddler Ray, Port Jackson Shark, Cat Shark, Butterfly Perch, Goatfish, Moonlighter, zoanthids, and soft corals. The site requires boat access and is suited for intermediate divers due to potential surge and current hazards.

Cottage by the Sea is a shallow reef located 100 metres offshore from Portsea. This site features depths between 6 and 10 metres, with an average of 8 metres, making it suitable for beginners. Divers and snorkellers can expect visibility ranging from 10 to 30 metres. Access is via a shore entry, though users should shuffle their feet in the shore break to avoid stingrays. Conditions include moderate currents and potential boat traffic, requiring the use of a surface marker buoy. Water temperatures fluctuate between 13C and 19C throughout the year. Parking is available at the site, and night diving is permitted.

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.

Spectacular Reef in Sorrento is a wall and drop-off site located 1000 metres offshore within a major shipping channel. The topography features shallow sections at 6 to 9 metres, with the main reef dropping to depths between 15 and 33 metres. Due to strong tidal currents, this site must be dived at slack water and is suitable for advanced divers only. Visibility ranges from 3 to 20 metres. Divers should be aware of significant boat traffic and use a surface marker buoy during ascent. The reef structure is characterised by ledges and crevices that support soft corals and sponges.