The Portland Maru is the largest wreck on Kangaroo Island and the island's best wreck dive. A 5,865-ton, 385 ft Japanese steel steamer built in 1919, she struck an unidentified object in 1935 and began to settle by the bow; her master beached her near Cape Torrens on the north-west coast, about 11 km east of Cape Borda, to save the ship. She could not be saved and was broken up by the sea over the following decades.

DEW's shipwreck trail notes that the site offers rewarding experiences for divers, with the remains lying in about 15 m, 200 m offshore, including visible boilers, engine, propeller shaft and winches. The Marine Life Network puts it about 500 m offshore at 16 m, with visible hull remains, two boilers and the steam engine, and heavy fish concentrations. The machinery stands proud of the reef and is encrusted with sponges and algae, and the wreckage has become an artificial reef for snapper, old wives, boarfish, blue devils and schools of bullseyes and sweep.

Cape Torrens, just east, has the highest coastal cliffs in South Australia (263 m), and the setting beneath them is spectacular. Access is only by boat along the remote north coast, and the site depends on calm southerly weather. As a protected historic shipwreck, nothing may be removed. The dive suits Open Water divers comfortable with boat diving; the moderate depth allows a relaxed exploration of the whole debris field in one dive. Bring cylinders from Kingscote and plan a full day.

Take the SeaLink ferry from Cape Jervis to Penneshaw (45 min), then drive west via Kingscote and the North Coast Road; the western north-coast sites are 1-1.5 hours from Kingscote on partly unsealed roads (red dirt, corrugations). The wreck lies off the cliffs near Cape Torrens (11 km east of Cape Borda) and is reached by boat along the north coast – the closest launching is at Stokes Bay or via a Kingscote operator on longer trips. Anchor in sand beside the wreckage in calm southerly weather.

Kangaroo Island's north coast faces Investigator Strait and is sheltered from the prevailing south-westerly Southern Ocean swell, so it is the island's most reliable diving coast. It is exposed to northerly and north-westerly winds and swell, which bring surge, poor visibility and dangerous entries – dive on southerly to south-easterly winds or after a few days of southerlies. Summer and autumn have the most settled weather; winter fronts bring north-westerlies before they pass.

Visibility is often 10-20 m in good conditions. Mornings are calmer before sea breezes.

Descend to the boilers, then follow the line of machinery – engine, propeller shaft and winches – and scattered hull plates across the reef at about 15 m, circling back to the anchor.

Protected historic shipwreck – no souveniring; no penetration possible (broken up).

Kangaroo Island Dive & Adventures (Kingscote) – guided north-coast boat and shore dives (confirm current trading); otherwise private boats. Part of the DEW Kangaroo Island Shipwreck Trail.