Off Cosy Corner lie small islands surrounded by reef that marinelife.org.au describes as more easily accessed from the Hamelin Bay boat ramp than as shore dives, with good diving on the lee sides of the islands in suitable weather. It lists schools of buffalo bream, black-headed puller, coralfish, old wives, herring cale, trevally, banded sweep and zebrafish.

Those schooling fish suggest healthy, current-fed reefs, and the islands provide the shelter that is otherwise scarce on this coast. Kelp and weed cover the shallower reef, with ledges and gutters below.

The site suits Open Water divers with a small boat and some experience in the South West's changeable conditions. Published detail is limited, so depths and positions are indicative, and local knowledge will help identify the best lee-side spots on the day.

Combine it with the Hamelin Bay wrecks and Hamelin Island for a day of boat diving from the same ramp.

The coast around Cape Leeuwin is where the Indian and Southern oceans meet, and it is one of the most exposed shorelines in Australia. The sheltered coves and bays near Augusta are the exceptions, which is why local divers value them. There is no dive shop in Augusta, so bring filled cylinders from Busselton or Perth, and remember that the nearest recompression chamber is at Fiona Stanley Hospital in Perth, about four hours' drive away. Ngari Capes Marine Park zoning includes sanctuary zones at Cape Leeuwin and East Flinders Bay, so check the maps before fishing or collecting. Allow for the run back to Hamelin Bay if the sea breeze arrives early.

More easily reached by boat from the Hamelin Bay ramp than by shore dives (marinelife.org.au); run south along the coast to the islands off Cosy Corner and anchor in their lee. Boat ramps along Geographe Bay include Bunbury (Casuarina), Busselton, Port Geographe, Quindalup and Dunsborough; on the Capes coast the Canal Rocks, Gracetown and Hamelin Bay ramps are small and swell-exposed. Check the forecast, carry a marine radio and log a trip plan with the local Marine Rescue group.

The lee sides of the islands offer good diving in suitable weather; the windward sides are exposed to the Indian Ocean swell. Calm summer and autumn mornings only. General pattern on the Capes and Leeuwin coast: summer mornings often have light easterly (offshore) winds before a south-westerly sea breeze, and long-period south-westerly groundswell can arrive on otherwise calm days; winter fronts bring big swell and north-westerly winds.

Check the Bureau of Meteorology swell forecast, not just the wind.

Anchor in the lee of an island, explore the surrounding reef and ledges, and stay on the sheltered side. Agree a turn pressure before descending (half gas, or a third where current is likely), carry a DSMB, and make a 3-minute safety stop at 5 m.

No operator; private boats from Hamelin Bay. Nearest dive services: Swan Dive (Busselton/Port Geographe) for fills, hire, nitrox and charters; no dive shop in Margaret River or Augusta.