TT Seawise Giant—formerly Oppama; later Happy Giant, Jahre Viking, Knock Nevis, and Mont—was a ULCC supertanker and the longest self-propelled ship in history. It was built in 1974–1979 by Sumitomo Heavy Industries in Yokosuka, Kanagawa, Japan. Seawise Giant's engines were powered by Ljungström turbines. The ship possessed the greatest deadweight tonnage ever recorded. Fully laden, her displacement was 657,019 tonnes.