Marmion Marine Park, declared in 1987 as Western Australia's first marine park, stretches about 20 km from Trigg Island to Burns Beach and protects more than 136 fish species, ten seagrass species and 21 seabird species. Wanneroo Reef is one of the named inshore reefs that DBCA lists as boat-access dive sites within the park, along with Cow Rocks, Whitfords Rock, Wreck Rock and the Centaur wreck. The park guide describes these reefs as enticing divers with intricate overhangs, ledges, caves and swim-throughs.

Like the other inshore reefs, Wanneroo Reef is limestone rising from sand and seagrass. Its top carries kelp and algae, and its edges are undercut. Expect buffalo bream, wrasse, scalyfin, western blue devils, old wives, morwong and leatherjackets, with western rock lobster and Port Jackson sharks under the ledges, sponges and small corals on the walls, and rays on the sand. Australian sea lions pass through the park.

It is now a separate row. Its depth and exact position should be checked with local operators before diving.

The reef suits Open Water divers looking for a relaxed boat dive close to Hillarys, particularly when the offshore reefs are too rough. Carry a surface marker buoy, as boats use the area heavily on weekends.

Because the inshore reefs are close to the harbour, dives here are short trips that suit an early start and a return before the sea breeze.

Launch at Hillarys Boat Harbour (public ramps off Southside Drive) or the Ocean Reef boat ramp further north. Wanneroo Reef is one of the inshore reef lines, a few minutes' run from the harbour entrance. DBCA lists it as requiring boat access.

Anchor in sand beside the reef and observe any sanctuary zone boundaries. Hillarys Boat Harbour has parking, toilets, fuel and dive shops, and it is about 25 minutes from the Perth CBD via the Mitchell Freeway and Hepburn Avenue.

Marmion's reefs are exposed to south-westerly and westerly ocean swell and to the afternoon south-westerly sea breeze (the Fremantle Doctor), which in summer usually arrives between late morning and early afternoon. Dive in swell under about 1.5 m with light easterly winds and before the sea breeze. Inshore visibility is lower than at the outer reefs and falls after swell.

Anchor in sand beside the reef, follow its edge looking into overhangs and caves, then return along the top to the anchor.

Included occasionally in Marmion boat dives by Hillarys-based operators; private boats.