Sorrento Back Beach sits on the open Bass Strait coast of the Mornington Peninsula, a few kilometres south of the Sorrento township. The reef drops to around 12 m and is heavy with kelp, sponges and the usual south-coast crew — crayfish, abalone, weedy seadragons, blue devils and sweep schools. Shore entry is through the surf zone at the main beach steps, which means you need a flat day. South or south-west swell shuts it down quickly, so look for swell under a metre, light northerly winds and a tide near slack. Easy parking at the lookout car park, short walk to the water. Use the live 7-day wind and swell forecast on this page to find your window. Intermediate divers only — surf entry, exposed swell, watch the rip down the eastern end of the beach.
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.