Blowhole & Thunder Point, Lady Julia Percy Island

Meet the site

Thunder Point is the south-eastern corner of Lady Julia Percy Island, the point that takes the brunt of the Southern Ocean swell, and the Blowhole is the sea cave that gives it its name. In ordinary weather every swell that hits the point drives water into a cave in the cliff and blows it out through the roof with a boom that can be heard across the island; on the rare day when the sea is glassy, the Scuba Doctor records, there is underwater an 18 m wide opening to a magnificent cave penetrating deep under the island. Few have ever seen it and fewer have dived it, and the site guide calls it a truly awesome experience. The entrance lies on a basalt wall dropping into 25 m, and the wall itself, in cold upwelled water, is heavily encrusted with sponges and ascidians and patrolled by the island's seals and its schools of sweep, butterfly perch and boarfish. Leopard Seal Reef, with its giant underwater rock pools, lies a few hundred metres to the north-east along the same southern cliffs.

This is an expedition dive in every sense. It requires a flat calm on the most exposed side of an island 8 km offshore, a boat skipper willing to hold position under the cliff, and divers with cavern experience, lines and lights who understand that a swell arriving while they are inside would be lethal. Nobody should plan a trip around it; it is something to be attempted when a party already at the island for the walls and seals finds the point silent and the sea like glass. For the diver who gets that day, it is one of the most extraordinary places on the Victorian coast, a cave under a seal island that almost nobody has entered. The island is a Wildlife Reserve and Indigenous Protected Area, landing is prohibited without a permit, and great white sharks frequent the colony.

What you might see

Australian fur seals, sea sweep, butterfly perch, longsnout boarfish, southern rock lobster, sponges and ascidians on basalt, bull kelp on the shallow rim, occasional great white sharks

Location

A sea cave at Thunder Point on the south-eastern end of Lady Julia Percy Island whose 18 m wide underwater entrance penetrates deep under the island; it blows at the surface in any swell.

Facilities nearby

Boat ramps at Port Fairy and Yambuk; nothing on the island; air in Warrnambool or Portland.