SHANGHAI - The Chinese salvage ship Dali returned to Shanghai on Wednesday after working 590 days to hoist the sunken Sewol ferry in the Republic of Korea (ROK).

Sewol, lying some 44 meters deep on the sea bed, was raised from the waters off the southwest coast of the ROK on March 25, some three years after it sank in April 2014 with 476 people on board.

Together with support vessels, the 2,500-tonne floating crane Dali was sent to the ROK in August 2015 by Shanghai Salvage Company to fulfill the salvage mission.

The Chinese state-run company won the bid to carry out the operation in an open tender issued by the ROK government in July 2015.

Around 60 workers arrived to Shanghai with the Dali. More than 90 Chinese personnel still remain in the ROK with another salvage ship, Shenqian, which will return later, company officials said.

More than 300 people were left dead when Sewol capsized. A total of 295 bodies were recovered, while nine remained unaccounted for.

Deputy director of Shanghai Salvage Jiang Yan said it was extremely difficult to lift the ship, which fell on its left side, tilting 90 degrees.

Divers and workers were also challenged by poor visibility and unpredictable waters, he said.