The Mylor Star is the most recent wreck on the Investigator Strait Shipwreck Trail. She was a steel-hulled motor fishing vessel built in 1978, working the productive waters at the mouth of Spencer Gulf. On 9 June 1982 she was caught in a storm near Althorpe Island; while the skipper was trying to reposition the boat, her reverse gear failed and she was driven onto the south-west corner of the island.

Both crew survived. The Department for Environment and Water records the wreck in 12-15 m, with only about half the hull visible – the rest broken up or buried by the violent swell that sweeps this corner of the island. What remains is a low steel structure among boulders and kelp, gradually being colonised by sponges and algae, with blue groper, sweep, old wives and other reef fish sheltering nearby.

Seals from the Althorpe colonies are frequent visitors. The wreck itself is modest and, by most accounts, in poor condition. Its interest lies in its place on the trail, the dramatic setting under Althorpe's cliffs and the reef life around it.

It sits on the most exposed side of an exposed island, so it can only be dived on the calmest days of the year. It suits experienced divers completing the shipwreck trail or exploring Althorpe, and is best combined with a wall dive or Seal Cove on the same trip. Given the depth and exposure, plan it as the first dive of the day while the sea is flattest, and keep a tender on the boat.

From Adelaide drive about 300 km (3.5 hours) via Port Wakefield, Minlaton and Warooka to Marion Bay; Dhilba Guuranda-Innes National Park begins just west of the township (vehicle entry fee, pay online or at the Stenhouse Bay visitor centre). Launch at Marion Bay and cross about 22 km south-west to the south-west corner of Althorpe Island (45-55 minutes). This is the most exposed side of the island, facing the open Southern Ocean, so it can only be dived in genuinely calm conditions.

Use the DEW coordinates and a shot line.

The southern tip of Yorke Peninsula faces the open Southern Ocean and Investigator Strait, so south-westerly and southerly swell is the controlling factor: most exposed sites need swell under about 1.5 m and are best after several days of northerly or north-easterly winds, which blow offshore along this coast. Winter cold fronts bring big south-westerly swell and strong winds and can close the area for days. Summer afternoon south-easterly sea breezes make boat runs rough, so launch early.

Visibility is typically 10-20 m in settled conditions but drops sharply with swell-driven surge. The south-west corner of Althorpe takes the full Southern Ocean swell; wait for swell under 1 m and light winds.

Descend the shot to the hull at 12-15 m, inspect the visible half of the vessel and surrounding reef, and return to the shot. Keep the dive short and carry an SMB for drift pick-up.

No regular operator; very occasionally dived by private boats and clubs on Althorpe expeditions.