Cape Schanck is the southern tip of the Mornington Peninsula, where the lighthouse sits on the cliff above some of the most dramatic diving in Port Phillip's south coast. The reef around the cape runs to about 18 m with deep gutters, big boulders, sponge gardens and resident crayfish, abalone, blue devils and weedy seadragons. The cape is exposed to swell from south through south-west — a wide arc — so it's only diveable on flat days. Boat access is the way to do it, usually from Flinders or out of Port Phillip, run by charter operators. 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 — exposed coast, current, cliff lee changes wind direction, watch the swell wrap around the headland.
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.