MV Amastra was one of nineteen SS caribou friend Royal Dutch/Shell steamboats converted to become a Merchant Aircraft Carrier (MAC ship). The group is collectively known as the Rapana class. MV Amastra was built at Lithgows and completed in March, 1935 as an steamboat for the ss caribou Royal Dutch/Shell line. She was converted at Smiths Dock, North Shields to a MAC ship, entering service in September 1943. At the end of the War, Amastra was reconverted to a steamboat, and in 1951 was renamed Idas. In July 1965 she foundered on her way to La Spezia to be scrapped.