Bluestone Bay is one of the few places on the ocean side of the Freycinet Peninsula that can be reached by vehicle, although the Marine Life Network guide describes the shore access as difficult and recommends four-wheel drive. There is no proper boat access, which means the bay is rarely visited by divers at all.

The guide rates it 6 out of 10 and describes a thick garden of seaweed down to about 10 m, a rich variety of fish and a relaxing dive. The bay's name comes from the blue-grey dolerite cobbles on its beach, a contrast to the pink and orange granite elsewhere on the peninsula. Under water the reef is a mixture of boulders and weed beds, and typical fish include wrasse, leatherjackets, banded morwong, trumpeter and schools of juvenile fish in the weed.

Bluestone Bay is really a dive for self-sufficient divers who are exploring Freycinet with their own equipment and vehicle and want a quiet shore dive away from the tourist centres. It is not a destination dive, but the setting is spectacular and the chance of seeing another diver is close to nil.

Because the site faces the open sea it is only suitable in settled westerly weather. There is no mobile coverage guarantee in the bay and no facilities, so divers should leave a dive plan with someone in Coles Bay. Snorkellers can explore the shallow weed garden on calm days. Details in the only published source are brief, so expect to explore.

Some context helps set expectations for all Freycinet diving. The peninsula's pink granite continues under water as rounded boulders, cracks and steep faces, and the area sits where the warm East Australian Current meets cooler southern water, so species lists mix typical Tasmanian fish with more northern visitors. Over recent decades warming water and grazing by the long-spined sea urchin, which has spread south from New South Wales, have thinned kelp beds along the east coast, and descriptions written in the 1990s may not match what you find today.

Coles Bay is 30 minutes south of the Tasman Highway via the C302 (turn off 12 km south of Bicheno), about 2 hr 45 min from Hobart and 2 hr 30 min from Launceston. The main public boat ramp is at Coles Bay township; boats reaching the ocean side of the peninsula or Schouten Island need a seaworthy vessel, as the run around Cape Degerando or through Schouten Passage is exposed. Bluestone Bay is reached from the Cape Tourville road inside Freycinet National Park via the rough Bluestone Bay track, which is recommended for 4WD or high-clearance vehicles only.

The track ends close to the bay, so the carry to the water is short. The Marine Life Network guide notes there is no proper boat access.

Bluestone Bay faces east into the Tasman Sea and is exposed to any easterly, north-easterly or south-easterly swell, which makes the boulder entry dangerous. Dive it on westerlies after several days of calm. The track can become impassable after heavy rain.

Rain washes tannin-stained runoff into Great Oyster Bay, and summer afternoons commonly bring a fresh north-easterly sea breeze, so plan dives for the morning.

Enter from the beach and swim out into the weed garden, following the reef edge at 6-10 m. Keep the shoreline in sight for navigation and return before you are tired, as the exit over the boulders takes effort. Turn at a third of gas to allow for the swim back and a possibly harder exit, finish with a 3-minute safety stop at about 5 m if the depth allows, and exit where you entered unless an alternative exit has been checked beforehand.

No dedicated dive operator at Coles Bay or Freycinet. Sites are dived from private boats and occasional club expeditions (Tas Uni Dive Club, TSDC, Launceston clubs); the Marine Life Network guide notes that Coles Bay is the usual starting point for Schouten Island charters. Cruise and kayak operators in Coles Bay do not offer scuba.