Clef, also known as Skull Rock, is a granite island off the coast of Cape Wilsons in the Australian state of Victoria. It is part of the Anser group of three islands and is one of the most picturesque islands in the Wilsons-Promontory National Park.
On the western side of the island is a giant cavern with a grassy floor. Most likely, it was carved by the sea over the course of millennia, when the levels of the world’s oceans were much higher than the current ones. The cave is 130 meters wide, 60 meters high and 60 meters deep. From a certain angle, the island really looks like a skull — hence the appropriate nickname “Skull Rock”. The cave was also used by passing ships as a training ground for firing cannons.
There are actually two large caves on the western side of the island. The roof of the smaller cave is about 25 meters above the sea and forms the bottom of the upper larger cave, covered with soil and vegetation on the surface.
The island is virtually inaccessible to visitors, with high vertical cliffs and no place for a boat to dock. For this reason, very few people have set foot on the island and explored the cave. The lucky few who did so reported many cannonballs inside.
Birds, especially the Dark-skinned Great Cormorant, have chosen Clef Island because of its inaccessibility and lack of people. Clef Island has become their real home.