Seawise Giant, later Happy Giant, Jahre Viking, Knock Nevis, Oppama, and finally Mont, was a ULCC supertanker and the longest ship ever built. It possessed the greatest deadweight tonnage ever recorded. Fully loaded, its displacement was 657,019 tonnes (646,642 long tons; 724,239 short tons), the heaviest ship of any kind, and with a laden draft of 24.6 m (81 ft), it was incapable of navigating the English Channel, the Suez Canal or the Panama Canal. Overall, it was generally considered the largest ship ever built. It was sunk during the Iran–Iraq War, but was later salvaged and restored to service. It was last used as a floating storage and offloading unit (FSO) moored off the coast of Qatar in the Persian Gulf at the Al Shaheen Oil Field.
The vessel was sold to Indian ship breakers, and renamed Mont for its final journey in December 2009. After clearing Indian customs it was sailed to and intentionally beached at Alang, Gujarat, India, to be broken up for scrap.
Seawise Giant was ordered in 1974 and delivered in 1979 by Sumitomo Heavy Industries, Ltd. at its Oppama shipyard in Yokosuka, Kanagawa, Japan as a 418,611 ton ULCC. The vessel remained unnamed for a long time, and was identified by its hull number, 1016. During sea trials, 1016 exhibited massive vibration problems while going astern. The Greek owner refused to take delivery and the vessel was subject to a lengthy arbitration proceeding. Following settlement the vessel was sold and christened Oppama by S.H.I.
The shipyard exercised its right to sell the vessel and a deal was brokered with Hong Kong Orient Overseas Container Line founder C. Y. Tung to lengthen the ship by several metres and add 146,152 metric tons of cargo capacity through jumboisation. Two years later it was relaunched as Seawise Giant.
After the refit, the ship had a capacity of 564,763 tonnes deadweight (DWT), a length overall of 458.45 m (1,504.1 ft) and a draft of 24.611 m (80.74 ft). It had 46 tanks, 31,541 square metres (339,500 sq ft) of deck space, and drew too much water to pass through the English Channel. The rudder weighed 230 tons, the propeller 50 tons.
Seawise Giant was damaged and sunk during the 1980–1988 Iran–Iraq War by an Iraqi Air Force attack while anchored off Larak Island on 14 May 1988 and carrying Iranian crude oil. The ship was struck by parachute bombs. Fires ignited aboard the ship and blazed out of control, and it sank in the shallow waters off the coast of Larak Island, Iran. It was declared a total loss and was written off.
Shortly after the Iran-Iraq war ended, Norman International bought the shipwreck, salvaged and repaired it. It was renamed Happy Giant after the repairs. These repairs were done at the Keppel Company shipyard in Singapore after towing it from the Persian Gulf. It entered service in October 1991 as Happy Giant.
Jørgen Jahre bought the tanker in 1991 for US$39 million and renamed it Jahre Viking. From 1991 to 2004, it was owned by Loki Stream AS and flew the Norwegian flag.
In 2004, it was purchased by First Olsen Tankers Pte. Ltd., renamed Knock Nevis, and converted into a permanently moored storage tanker in the Qatar Al Shaheen oil field in the Persian Gulf.
Knock Nevis was renamed Mont, and reflagged to Sierra Leone by new owners Amber Development Corporation, for its final voyage to India in January 2010 where it was scrapped by Priyablue Industries Pvt. Ltd. The vessel was beached on December 22, 2009. Its 36 tonne anchor was saved and sent to the Hong Kong Maritime Museum for exhibition.
Seawise Giant was the longest ship ever constructed, at 458.45m, longer than the height of many of the world's tallest buildings, though slightly smaller than Taipei 101's 509 m (1,670 ft), it was larger than the Petronas Twin Towers' 451.9 m (1,483 ft).
Despite its great length, Seawise Giant was not the largest ship by gross tonnage, ranking fifth at 260,941 GT, behind the four 274,838 to 275,276 GT Batillus-class supertankers. It is the longest and largest by deadweight: 564,763 metric tons. Batillus-class ships and Seawise Giant were the largest self-propelled objects ever constructed.
Seawise Giant was featured on the BBC series Jeremy Clarkson's Extreme Machines while it was underway as Jahre Viking. According to its captain, S. K. Mohan, it could reach up to 16.5 knots (30.6 km/h) in good weather, it took 9 km (5 1⁄2 mi) to stop from that speed, and its turning circle in clear weather was about 3 km (2 mi).