The Clan McMaster, a cargo vessel of 6,563 tons, was wrecked on 30th September 1923 on her way from Glasgow to Liverpool, ultimately heading for the Far East. She was part-loaded with heavy and light machinery, sewing machines, cotton goods, and 2,000 tons of coal. In dense fog, the ship was caught in the currents and driven onto the rocks in Blind Sound - the area between Thousla Rock and the Calf.

All 80 crewmembers were able to reach the safety of the Calf. On returning to the ship the next day, the crew realised that much of the movable property (including the sewing machines) had already been taken.

On the arrival of the Liverpool salvage ship Ranger, it was possible to rescue some of the light goods from the hold, however, the ship was settling even deeper into the water. The ship became a total loss and within a year the Clan McMaster had disappeared into the sea where its wreckage, engines and boilers still lie.