The shipyard then exercised its right to sell the ship. A deal was brokered with Hong Kong shipping magnate C. Y. Tung, founder of the shipping line Orient Overseas Container Line. A deal was reached, but Tung required the ship's size be increased by several metres in length and 87,000 metric tons of cargo capacity by jumboisation. Two years later, the vessel was launched and named Seawise Giant.
From 1979 to 2004, she was owned by the company Loki Stream AS. During this period she flew the Norwegian flag.
In this period, she was renamed Happy Giant from 1989 to 1991.
Jorden Jahre bought the ship in 1991 for the sum of US$39 Million. It was at this stage that the ship was renamed Jahre Viking. It was sold in 2004.
The ship was damaged during the Iran–Iraq War while transiting the Strait of Hormuz. As a result she was declared a total loss and laid up in Brunei. At the end of the war, she was towed to the Keppel Company shipyard in Singapore, repaired, and renamed Happy Giant. The ship was sailing again in October 1991.
In 2004, she was bought by First Olsen Tankers Pte. Ltd., renamed Knock Nevis and converted into a permanently moored storage tanker.On November 30, 2004 the conversion to FSO was completed. The ship is now permanently moored in the Qatar Al Shaheen oil field in the Persian Gulf, operating as an FSO.
In terms of length, Knock Nevis has a length overall of , making her the largest ship ever constructed. The vessel is longer than many of the world's tallest buildings are tall, for example the Petronas Twin Towers at . She is smaller than the Sears Tower at , and Taipei 101 at , and considerably smaller than the skyscraper Burj Dubai, currently under construction, at .
Knock Nevis is not the largest ship in all measures, though. By gross tonnage, for example, she ranks fifth, at 236,710 GT, behind the four Batillus class supertankers which range from 274,838 to 275,276 GT. These ships are the largest self-propelled objects ever constructed.