Skull Rock: The Almost Inaccessible Australian Sea Cave That Only Nine People Have Ever Entered

People keep saying that more humans have walked on the moon than have been inside Skull Rock. That is, as far as anyone can verify, completely true. Twelve people have walked on the moon. Nine people have entered Skull Rock. The moon is 238,855 miles away. Skull Rock sits just 2.7 miles off the coast of Victoria, Australia.

The reason for that gap is not distance. It is the fact that Skull Rock is one of the most physically inaccessible places on Earth that is also, somehow, not technically in the middle of nowhere.

What Skull Rock Actually Is

Skull Rock’s official name is Cleft Island, and it sits among the Anser Group of islands just off the southwestern coast of Wilsons Promontory, the southernmost point of the Australian mainland. From a boat at the right angle, it looks exactly like a skull: a massive granite cranium, a cave that reads as the eye socket, and the ridge of a nose below it. The resemblance is immediate and slightly unnerving.

The cave itself is enormous. It measures roughly 430 feet wide, almost 200 feet tall, and 200 feet deep. To give that some scale, the Sydney Opera House would fit inside it. The cave floor sits about 100 feet above sea level, covered in a thick carpet of grass and soil that makes the whole thing look even more surreal from above. Nesting seabirds pack the interior walls. A fur seal colony occupies the granite ledges outside. The surrounding waters of Bass Strait hold the wrecks of several ships that misjudged the approach over the years.

All of this is completely inaccessible by conventional means. Vertical granite cliffs ring the entire island, ranging from 100 to nearly 200 feet high, with no ledge wide enough to land a boat and no surface gentle enough to climb without serious technical equipment. The Bass Strait is notoriously rough water. Even in calm conditions, waves crash against the base of the cliffs hard enough to make any approach dangerous.

How the Nine Got In

The only documented way anyone has successfully entered the cave is by helicopter.

You land on the very top of the rock, which is itself not a straightforward proposition given the wind patterns around the island. Then you abseil down ropes from the summit into the cave below. The process requires helicopter access, technical climbing equipment, and enough experience with both that you are not likely to die on the way down.

The first recorded entry happened in 1972, when a team visited on behalf of the Victorian National Parks Authority and wrote up a report about what they found. Prior to that visit, the report notes, it is quite certain that no person had ever entered the cave. One person had previously managed to reach the top of the rock, but the cave itself remained completely unvisited.

Inside, the 1972 team found nesting birds, no mammals, and several lumps of heavily oxidized iron they initially mistook for ore. On closer inspection, the lumps turned out to be old cannonballs, roughly cast and degraded almost beyond recognition. The most likely explanation is that passing ships used the rock as target practice over the centuries. By whom and when exactly remains unknown.

In 2015, Scottish historian and television presenter Neil Oliver visited with a film crew and a team of climbers for the Australian television series Coast Australia. Oliver later described it as the most special place he had ever seen. His team reportedly found additional cannonballs in various states of decay, confirming the earlier finding without resolving where they came from.

Why It Stays That Way

Cleft Island sits within Wilsons Promontory National Park, which applies strict protections to the island and its surrounding waters. The seabird colonies inside the cave make it a significant breeding habitat, and Parks Victoria tightly restricts access to protect them. In practice, even getting permission to attempt an entry is extremely difficult, and the physical requirements on top of that narrow the pool of possible visitors even further.

Tour boats do run out to the island from nearby Tidal River and from Port Welshpool, and getting up close on the water is a completely different experience from viewing it from the shore. At close range the scale of the cave becomes genuinely disorienting, and on a good day seals carpet the lower ledges in numbers that feel almost theatrical. You just cannot get off the boat.

The nine people who made it inside have all described the experience as completely unlike anything else they have encountered. A grassy floor inside a granite cave 100 feet above Bass Strait, surrounded by nesting birds and the sound of wind moving through an opening the size of a city block. Cannonballs on the floor from ships that fired at it decades or centuries ago for reasons nobody recorded.

Most of us are going to see it from a boat, which is still worth doing. The skull shape from the right angle is exactly as good as advertised.