Black Reef lies in the approaches to Recherche Bay, about 8 km from the Catamaran River ramp and halfway between Actaeon Reef and the mainland. The Marine Life Network guide describes dark patches of kelp visible from the surface, with bull kelp in the shallows and Macrocystis gardens deeper, over a scoured bottom with rocky outcrops, in 4-6 m. It notes that the reef is hard to see at high tide in calm weather but shows a noticeable surface break in swell, and that it is exposed to southerly swell.

Bull kelp (Durvillaea) is a sign of wave exposure: its thick, leathery fronds thrash in the surge and create a dynamic, noisy shallow zone. Deeper, the giant kelp – if still present, given regional declines – provides a softer, more sheltered forest where fish gather. Wrasse, leatherjackets, magpie morwong and bastard trumpeter are likely, along with abalone and sea urchins on the scoured rock.

It is a remote, weather-dependent site for divers with a capable boat, and it combines with Actaeon Island or Sterile Island on the same trip. Take care approaching the reef in a boat; submerged rock close to the surface is a real hazard. The far south has no dive shop or air fills – bring filled cylinders from Hobart or Kingston – and mobile coverage is patchy, so carry a VHF radio and leave a trip plan.

Visibility can be excellent on calm days, when clean Southern Ocean water sweeps across the reef, and the swaying kelp makes for atmospheric wide-angle photography.

Recherche Bay is at the end of the Huon Highway and the gravel road beyond Southport and Lune River, about 2 hours (110 km) south of Hobart; it is Australia's southernmost road-accessible coastline. The Catamaran River boat ramp at the southern end of the bay is the usual launch; Cockle Creek has camping and is the start of the South Coast Track. The Marine Life Network guide places Black Reef about 8 km from the Catamaran River ramp, halfway between Actaeon Reef and the mainland – roughly 20-25 minutes by boat.

It is hard to see at high tide in calm weather but shows a surface break in swell; approach carefully with a sounder.

The far south – Port Esperance, Southport and Recherche Bay – opens southward to the Southern Ocean. Southerly and south-westerly swell and strong southerly winds make the exposed sites unworkable and quickly reduce visibility, while northerly and light westerly winds give calm water. Sheltered bays such as Port Esperance and inner Recherche Bay remain diveable in moderate conditions.

Weather changes rapidly and fronts arrive every few days; plan around high-pressure systems in late summer and autumn and watch for south-westerly changes. Black Reef is exposed to southerly swell, which breaks on it; dive only in calm conditions.

Anchor off the reef in sand, swim through the bull kelp on the shallow top only if there is no swell, then explore the Macrocystis on the deeper flanks and the scoured bottom with rocky outcrops.

No regular operator; private boats and club expeditions. Underwater Adventures Tasmania runs occasional far-south trips (the Acteons are mentioned by Go Dive Tasmania as a kelp-diving area).