West Bay is the second documented site at Wedge Island, the largest of the remote Gambier Islands. The Marine Life Society of South Australia describes sheer walls and deep ledges in places, with moderately large boulder-covered crevices on the south side, in 10-25 m, and calls it spectacular but distant. The invertebrate life is rich: sponges, nudibranchs, small gorgonians, zoanthids and soft corals decorate the walls, and the Society records horseshoe leatherjackets, western blue groper, southern blue devils, leafy seadragons, stingrays and spotted catsharks.

Water clarity at the Gambiers is often exceptional, as the islands sit in oceanic water at the mouth of Spencer Gulf. Like the rest of Wedge Island, West Bay is an expedition dive – a long open-ocean crossing from Pondalowie Bay, strong currents, no nearby help and depths that reward careful planning. Very few divers ever reach it, which is part of its appeal.

It suits highly experienced divers with a large, well-equipped boat and a flexible schedule to wait for weather. Combine it with Shark Cove (see Wedge Island) on the same trip. Because the crossing takes well over an hour each way, most groups plan two dives and a surface interval in the lee of the island, and carry spare fuel, a satellite beacon and full first-aid and oxygen kits.

The reward is a seldom-seen reef where fish show little fear of divers and where the only other visitors are seals, dolphins and seabirds from the island colonies.

From Adelaide drive about 300 km (3.5 hours) via Port Wakefield, Minlaton and Warooka to Marion Bay; Dhilba Guuranda-Innes National Park begins just west of the township (vehicle entry fee, pay online or at the Stenhouse Bay visitor centre). Launch at Pondalowie Bay and cross about 25-30 km west to Wedge Island (1-1.5 hours), then round to West Bay. The Marine Life Society describes it as spectacular but distant, requiring you to pick your day and have a big boat.

The island is privately leased; do not land without permission.

The southern tip of Yorke Peninsula faces the open Southern Ocean and Investigator Strait, so south-westerly and southerly swell is the controlling factor: most exposed sites need swell under about 1.5 m and are best after several days of northerly or north-easterly winds, which blow offshore along this coast. Winter cold fronts bring big south-westerly swell and strong winds and can close the area for days. Summer afternoon south-easterly sea breezes make boat runs rough, so launch early.

Visibility is typically 10-20 m in settled conditions but drops sharply with swell-driven surge. West Bay faces the open ocean to the west; only dive it in a stable window of low swell, and ensure the forecast holds for the long return crossing.

Descend on the walls at 15-20 m and follow the ledges, then on the south side explore the boulder crevices before working up to 10 m for the end of the dive; tender follows SMBs.

No commercial operator; private expeditions only.