Flinders Cray Reef is the offshore reef that lies about 2 km off Flinders Back Beach in Bass Strait, just outside the boundary of the Mushroom Reef Marine Sanctuary, in 6–20 m. The Scuba Doctor lists it, like its counterparts off Cape Schanck and the Sorrento back beach, as a crayfishing reef with incredible ledges and overhangs that is equally good for exploring, fish-watching and photography. The reef is the same mixed basalt and limestone that forms West Head and Mushroom Reef, and its structure is a sequence of ridges and undercut ledges with kelp gardens on top and heavy sponge, bryozoan and sea tulip growth beneath.

Southern rock lobsters shelter in the overhangs, blue devils and Port Jackson sharks in the darker holes, weedy seadragons along the kelp margins, and the water column carries schools of sweep, zebrafish and old wives with morwong, boarfish, magpie perch and bluethroat wrasse on the rock; proximity to the sanctuary probably helps the fish numbers. Fur seals from the Seal Rocks colony off Phillip Island and dolphins are frequent visitors, and in winter whales pass close to West Head. It is an easy boat run from the Flinders ramp on a calm day and a dangerous one on any other, since the passage rounds West Head where the Western Port tide meets Bass Strait swell.

There is no charter, no mooring and no marker, so this is a dive for divers with their own capable boat, an accurate GPS mark and a settled forecast. It pairs with Flinders Pier for an easy second dive and with Mushroom Reef for the ecologically minded. Flinders Cray Reef suits Advanced divers comfortable in open water, lobster hunters observing Victorian regulations (season, size, licence, and strictly outside the sanctuary), and photographers wanting ledges of colour in clean water.

Launch at the Flinders boat ramp beside Flinders Pier and run south-west around West Head into Bass Strait – about 4 km, 10–15 minutes in a small boat but in open water once past the head. Anchor on the reef in 10–15 m (John Lawler's GPS mark is the published position) and descend the line. No charter schedules it; it is a private-boat and club site dived when the swell is low.

Best dived with minimal swell and a gentle northerly rolling through, in the source's words; the reef is open to every southerly and westerly swell in Bass Strait and the passage around West Head is rough with wind against the Western Port tide. Current on the reef is slight but the tidal stream through the Western Port entrance is strong close to the head, so give it room. Visibility is good ocean water, best in winter.

Descend the anchor to the reef top, follow the ledge line at 12–18 m checking every overhang for lobsters and blue devils, then return across the shallower reef at 8–10 m to the anchor and ascend the line with a safety stop; carry an SMB.

No regular operator – private boats and Peninsula dive clubs from Flinders ramp; The Scuba Doctor (Rye) can advise on marks.