The Marietta Dal was a 7500-tonne liberty ship built in the USA in 1944 and is one of the most interesting shipwrecks off Brisbane. On May 15 1950, the 140-metre-long ship was carrying a cargo of sulphur, oil, tractors and other general cargo when it ran aground on Smith Rock. Any hopes of salvaging the ship and cargo were quickly abandoned when the vessel broke in two.

Completely broken up, the remains of the Marietta Dal are now found in 10 metres to 18 metres and make for a fascinating dive. Scattered over a wide area of Smith Rock the main section of wreckage contains a twisted pile of plates, beams and the long prop shaft. However, the most interesting part of the wreck is the cargo of tractors, which look like small tanks with their caterpillar tracks. Even without the remains of the ship, this is a wonderful dive as there are ledges, caves and gutters packed with marine life.