The Osmanli was an iron-hulled screw steamer of 403 tons and about 180 ft, built in 1846, that was wrecked on Tinline Reef in D'Estrees Bay on Kangaroo Island's south-east coast in 1853. Remarkably, all 83 passengers and crew got ashore safely. DEW lists her on the Kangaroo Island Shipwreck Trail, 35 km south-west of American River, and a wreck register records large pieces of wreckage remaining in about 3 m, rating the diving as excellent.

As one of the earliest steamships wrecked in South Australia, the Osmanli is historically significant, and large iron sections still rest on the shallow reef, heavily encrusted and overgrown with algae and kelp. Reef fish – wrasse, sweep, leatherjackets, old wives – use the wreckage as shelter, and rock lobster hide beneath plates. The shallow depth makes it accessible to snorkellers as well as divers when conditions allow, and plenty of light reaches the site.

D'Estrees Bay is remote, reached by unsealed roads, and exposed to south-easterly swell, so a visit takes planning and a calm day. There are no facilities. The wreck is protected – look but do not disturb. It suits adventurous divers and snorkellers with an interest in early steamship history who are willing to travel to a quiet corner of the island. The bay also holds the ruins of an old whaling station and is a good place to see dolphins and seabirds, so a visit makes a full day out from American River. Carry spare water, fuel and a first-aid kit.

Take the SeaLink ferry from Cape Jervis to Penneshaw (45 min). From American River drive south-west about 35 km on unsealed roads to D'Estrees Bay on the south-east coast (4WD advisable on some tracks). The wreck lies on Tinline Reef; exact access points are not published, so ask locally.

Small boats can launch in the bay in calm weather; otherwise snorkel from shore when the swell is small.

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. D'Estrees Bay is partly protected from the south-west but open to south-easterly swell; the reef breaks in any sizeable sea.

Approach Tinline Reef in calm conditions, snorkel or dive among the large pieces of iron wreckage at 2-4 m, and keep clear of breaking water on the reef edge.

Protected historic shipwreck – no souveniring.

No regular operator – independent.