Lonsdale Wall sits inside Port Phillip Heads off Point Lonsdale and is widely rated among the best wall dives in Australia. The wall drops vertically from around 8 m to over 25 m, plastered in yellow zoanthids, sponge gardens, sea whips and gorgonians, with weedy seadragons, big bull rays, blue devils and crayfish hiding in the crevices. Like all Heads sites you dive it on slack water only — currents through the Rip can hit four knots — so timing is everything. Best window is 30 minutes either side of high or low tide in light northerlies and swell under a metre. Run by boat charter out of Queenscliff or Sorrento. This page shows the live 7-day wind and swell forecast plus the tide curve so you can pick your slot. Intermediate to advanced — current-aware divers only.
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.