Point Sir Isaac is the remote northern tip of the Coffin Bay Peninsula, reached by one of South Australia's classic 4WD tracks through Coffin Bay National Park. The Marine Life Society describes it as renowned for big swells and large fish on limestone reefs of moderate depth, about 10 m, and notes that big blue groper can be seen on every dive. The limestone reef here is sculpted by constant swell into ledges and gutters, with kelp and brown algae on top and sponges in the shaded overhangs.

Western blue groper, harlequin fish, sweep, old wives, silver drummer and magpie perch are typical, with crayfish in the cracks and dolphins and sea lions passing along the coast. The combination of access and swell makes Point Sir Isaac a true expedition site. The drive crosses tidal flats and soft beaches and must be timed with tides, and suitable diving days are rare.

Divers should be experienced, fully self-sufficient, and prepared to go home without diving if the sea is up. For those who make it on a good day, the reward is clear water, big fish and total solitude in one of the wildest parts of the state. Travel in convoy if possible, carry recovery gear, water and a satellite beacon, and let someone know your plans, as help may be many hours away.

From Coffin Bay township, the 4WD track through Coffin Bay National Park to Point Sir Isaac is long and scenic, crossing tidal flats and soft sand – allow several hours, lower tyre pressures and check tides. Alternatively, run by boat from Coffin Bay out through the inlet. Only attempt in calm, low-swell conditions.

The west coast of Eyre Peninsula faces the Great Australian Bight and receives almost constant south-westerly Southern Ocean swell; open-coast sites need swell under about 1.5 m and are only diveable a handful of days a month, usually after several days of northerly or easterly winds, which blow offshore. The large sheltered bays (Coffin Bay, Waterloo Bay, Venus Bay, Baird Bay, Streaky Bay, Denial Bay) are protected from swell and can be dived in most conditions except strong onshore winds. Summer brings strong afternoon south-easterly sea breezes; winter brings cold fronts with big swell but also calm, clear spells.

Water is cool: about 14-15°C in winter and 17-21°C in summer. Point Sir Isaac is renowned for big swells; wait for a clear window.

Enter in the lee of the point, explore the limestone reef at 8-10 m looking for blue groper, and return before swell or tide changes.

No regular operator; Coffin Bay Scuba Co. may advise; self-sufficient 4WD divers or private boats.