Cape du Couedic is the south-western tip of Kangaroo Island, marked by a lighthouse and one of the island's great natural sights: Admirals Arch, a rock arch weathered over thousands of years, beneath which lives a colony of long-nosed fur seals (formerly New Zealand fur seals). National Parks SA manages the site as part of Flinders Chase National Park, with a boardwalk and platforms that bring visitors close to the seals without disturbing them.

It is included here because divers ask about it and because it appears in lists of Kangaroo Island marine highlights. In practice it is not a dive site. There is no water access from the boardwalk, the coast faces the full Southern Ocean with heavy swell and surge most days, and entering the water around a breeding seal colony would disturb the animals and expose divers to risks from large male seals and from white sharks, which patrol seal colonies. The Western Kangaroo Island Marine Park covers these waters, and zoning should be checked for any activity. Nearby Weirs Cove, with the ruins of the lighthouse storehouses and flying fox, shows how difficult even landing supplies was here.

For divers, the best way to enjoy Cape du Couedic is on a rest day: walk the boardwalk, watch the seals playing in the arch's rock pools and surge channels, and then look for seals underwater at sheltered north-coast sites such as Western River Cove, where encounters are common.

Take the SeaLink ferry from Cape Jervis to Penneshaw (45 min). Drive about 2 hours from Kingscote to Flinders Chase National Park (entry fee applies), then follow the sealed road to Cape du Couedic lighthouse. A boardwalk and stairs lead down to the Admirals Arch viewing platforms above the seal colony.

There is no water access from the boardwalk and entering the water near the colony is unsafe and inappropriate. Any diving would require a capable boat in a rare calm; the arch may be closed in severe weather.

Kangaroo Island's south and west coasts face the open Southern Ocean and take the full force of prevailing south-westerly swells, commonly 2-5 m and bigger in winter. Diving is only possible in rare windows: swell under about 1-1.5 m, light northerly or north-easterly (offshore) winds and several settled days, most often in late summer and autumn (February-May). Rips and undertow are strong on the beaches, and wave surge reaches the bottom at recreational depths.

Conditions can change within hours as fronts arrive – check the Bureau of Meteorology coastal forecast and swell models, and have a sheltered north-coast alternative. Cape du Couedic is one of the most exposed points on the island; Admirals Arch and Remarkable Rocks may be closed in severe weather.

Not recommended. View the seals from the boardwalk. Any expedition dive would need to stay well away from the colony and haul-outs.

Not a recreational dive site. Respect marine mammal approach distances under SA regulations.

No operator – not a recreational dive site; viewing from boardwalk only.