into the sea floor. Gullfaks C Gullfaks C rests below the sea surface and has a total height of . Gullfaks C was the heaviest object that has ever been moved to another position, relative to the surface of the Earth with a total displacement between 1.4 and 1.5 million tons. Condeep platforms The original concrete structure of Sleipner A sank during trials in the Gandsfjord on August 23, 1991. A new structure was built, and deployed in 1993. Sources References Oil platforms