UK tech magnate Mike Lynch and five other people are missing after their luxury superyacht sank during a freak storm off Sicily, Italy's civil protection and authorities say. Lynch's wife and 14 other people survived. Lynch, who was acquitted in June in a big US fraud trial, was among six people who remain unaccounted for after their chartered sailboat sank off Porticello when a tornado over the water known as a waterspout struck the area overnight, Salvo Cocina of Sicily's civil protection agency said.

One body had been recovered, and police divers were trying to reach the hull of the ship, which was resting at a depth of 50 metres off Porticello, near Palermo, where it had been anchored, rescue authorities said. It had a crew of 10 people and 12 passengers, the Italian coast guard said. A sudden fierce storm had battered the area overnight, and struck the place precisely where the 56-metre UK-flagged Bayesian had been moored.

"They were in the wrong place at the wrong time," said Cocina, noting that another superyacht nearby was not as badly damaged and helped rescue some of the 15 survivors, who included Lynch's wife Angela Bacares. The Bayesian was notable for its single 75-metre-high mast - one of the world's tallest made of aluminium and which was lit up at night, just hours before it sank. Online charter sites listed it for rent for up to 195,000 euros ($A321,130) a week.

One of the survivors, identified as Charlotte Emsley, said she momentarily lost hold of her one-ye.