Beware Reef is the outstanding dive of East Gippsland's western half: an isolated granite reef rising abruptly from the sand 5 km off Cape Conran, whose exposed crest is about 70 m long and stands 2 m above water at low tide, and whose submerged structure continues about a kilometre to the south-east in 6–30 m. It was declared a 220 ha marine sanctuary in 2002 for the quality of its reef and the range of habitats packed into a small area, and Parks Victoria records more than 350 species here. The shallows are a bull kelp forest with sea urchins grazing the rock beneath; below the kelp the granite is covered in pink coralline algae and then, deeper, in gardens of finger sponges, sea fans, sea tulips and feather stars, with Maori octopus in the crevices.

The reef sits at the meeting point of Bass Strait and East Australian Current water, and its fish reflect that – trumpeters, wrasses, morwongs and sea sweep in schools, Port Jackson sharks and wobbegongs (a NSW species near its southern limit) under the ledges – while Australian fur seals haul out on the crest and join divers in the water. Beware Reef has also earned its name: the iron steamer SS Auckland (1871), the Ridge Park (1878) and the Albert San (1915) all struck it, and their scattered remains – boilers, plates, anchors and fittings – lie around the base of the granite and are protected as historic shipwrecks (the Auckland is a separate wreck dive). The sanctuary's isolation is its protection and its problem: the reef is exposed to every wind, the Cape Conran ramp is a fair-weather ocean launch, and there is no dive operator at Marlo, so it is dived by private boats and clubs on calm days only.

Divers who make the effort find the best combination of kelp, sponge garden, seals, sharks and wreckage in eastern Victoria, in water that is often clearer and warmer than anything to the west.

Launch at the Cape Conran ocean ramp (Joiners Channel on the western side of the cape, 18 km east of Marlo; Marlo is 15 km south of Orbost, 4.5 hours from Melbourne) and run about 5 km south-east – 15 minutes in a trailer boat. The ramp is exposed to south-westerly winds and swell and is usable only in calm conditions; Marlo's river ramp on the Snowy entrance is the alternative when the bar is safe. Anchor in sand off the reef, not on it, and note that the sanctuary is no-take and no-anchoring on reef.

There is no dive charter at Marlo; occasional trips are run from Lakes Entrance or by clubs.

Scuba Doctor notes that safe access is only possible in calm weather and that the reef is exposed to all wind directions, with the Cape Conran ramp itself exposed to south-westerlies; the reef breaks in any swell over about 1.5 m and the lee side shifts with the wind. Settled high-pressure days in late summer and autumn are the window, when East Australian Current water can push visibility past 20 m and temperatures to 21 °C. Winter brings clear but cold water and few calm days.

Dive the lee side and expect some current along the reef.

Anchor in sand on the lee side, descend and follow the base of the granite at 15–20 m along the reef's length, looking for the wreck fragments and the seals, then climb to the kelp-covered shallows at 6–10 m for the second half of the dive with the reef on the same shoulder, finishing under the boat. The reef extends about 1 km south-east underwater, so pick a section rather than trying to see it all.

No regular operator. Dived by private boats launched at Cape Conran and by Gippsland/Melbourne clubs (Dive La Trobe, SEADS) on occasional trips; Jeff Cross Diving Services (Lakes Entrance) has run trips by arrangement. Check current availability.