Skull Rock — also called Cleft Island — is the iconic granite monolith off the southern tip of Wilsons Promontory, with reef diving around its base out to about 30 m. It's one of the most photogenic dive sites in Bass Strait: a sheer rock wall rising straight out of the ocean, with kelp gardens, sponge cover, gorgonian fans, big crayfish, abalone, weedy seadragons, blue devils, schools of bullseyes and frequent fur seal encounters cruising past. Boat access only, on long charter trips out of Port Welshpool or by liveaboard. Best in light northerlies with swell under a metre and tide near slack. Use the live 7-day wind and swell forecast on this page to plan. Advanced divers only — exposed Bass Strait, strong currents around the rock, very remote location, multi-hour run from any port. Don't go without a settled forecast.
How far you can see underwater — measured in metres. 10m+ is great, 5–10m is workable, under 3m is murk. Driven by wind, swell, and recent rain.
Long-period waves rolling in from the open ocean. Direction matters more than height — a S swell hits Portsea hard, but an E swell rolls past. Period over 12 s = real ocean punch.
Offshore (N or NE) flattens the surface and clears the water. Onshore (SE through SW) chops it up and stirs sand. Calm or light offshore is the magic combo.
This site faces the open ocean. The exposure caption above shows which directions slam in. Anything from the opposite side gets blocked — that's the safest window.
Slack water — the 30 minutes either side of high or low — is calmest and clearest. Mid-tide brings the most flow. Plan to be down at slack, up before the run picks up.
Bass Strait sits 14–16 °C autumn–winter, 17–19 °C summer. Below 16° a 7 mm hooded keeps you warm for 60 min+. Drysuit if you're going long.