Seal Rocks off the south-west tip of Phillip Island is home to Australia's largest fur seal colony — around 25,000 animals — and on the right day the diving here is unforgettable. Reef sits in around 16 m and holds the usual south-coast lineup of crayfish, abalone, weedy seadragons and blue devils, but the real attraction is the seals themselves, which will buzz divers and roll past in big curious gangs. Boat access only, run by charter operators out of Cowes or Newhaven, with permits required to dive near the colony in some conditions. Best on light northerlies, swell under a metre and tide near slack. Use the live 7-day wind and swell forecast on this page to plan. Intermediate to advanced — exposed open coast, current around the rocks, and the seals demand respectful behaviour, give them space and let them come to you.
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.