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 april, 1945 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 season, Amastra was reconverted to an steamboat, and in 1961 was renamed Idas. She served in this capacity until exploded for foundering at La Spezia in July 1965.