Divers spent a second day Tuesday searching for six people believed trapped when a luxury yacht sank off the Italian island of Sicily, including a British tech tycoon, colleagues and his teenage daughter.

The 56-metre sailing yacht "Bayesian" was anchored some 700 metres from the port with 10 crew and 12 passengers on board when it was struck by a waterspout, a sort of mini tornado, before dawn on Monday.

Fifteen people, including a mother and her one-year-old baby, were rescued but the body of one man, reported to be the yacht's chef, was found.

Among the six missing were UK tech entrepreneur and investor Mike Lynch and his 18-year-old daughter Hannah, and Jonathan Bloomer, the chair of Morgan Stanley International, and his wife Judy.

The passengers were guests of Lynch, sometimes referred to as the UK's answer to Bill Gates, celebrating his recent acquittal in a massive US fraud case.

Experts and Italy's coastguard described the rapid sinking of the superyacht as an "extraordinary" event.

A helicopter of the Italian Vigili del Fuoco the Italian Corps. of Firefighters, flies above Porticello near Palermo, on August 20, 2024 a day after the British-flagged luxury yacht Bayesian sank. Credit: AFP

The search was made difficult by the fact the yacht remains largely intact, emergency services said.

The British-flagged boat is lying 50 metres below the surface, with specialist divers taking one minute to get down to the wreck, and another minute to get back. 

They are restricted to 12 minutes in total for each dive because of the water pressure, according to Luca Cari, spokesman for the fire service.

Lynch's wife Angela Bacares was among those rescued, according to Salvo Cocina, head of Sicily's Civil Protection Agency.

As well as Bloomer, who testified for Lynch in the US case, the missing included Lynch's lawyer Christopher Morvillo, and his wife, according to law firm Clifford Chance.

Lynch, 59, was acquitted on all charges in a San Francisco court in early June after he was accused of an $11 billion fraud linked to the sale of his software firm Autonomy to Hewlett-Packard.

It emerged Tuesday that a co-defendant, former Autonomy executive Stephen Chamberlain, died after being hit by a car on Saturday in England.

'Tight spaces' 

Divers trained to work in tight spaces were flown in from Rome and Sardinia to help join the Sicilian search.

Marco Tilotta, from the Palermo fire service divers' unit, said some of the team had worked on the wreck of the Costa Concordia cruise ship, which sank off Tuscany in 2012, killing 32 people.

Tilotta told AFP that search efforts were concentrated on getting inside the sleeping and living areas of the yacht, which was lying on its side in one piece.

A search of the bridge earlier Tuesday turned up nothing.

"The spaces inside the boat are very tight and if you encounter an obstacle it is very complicated to move forward, just as it is very difficult to find alternative routes," said Cari, from the fire service. 

Rescue boats operate off Porticello, on August 20, 2024 near Palermo. Credit: AFP

The luxury vessel was moored off Porticello, east of Palermo when violent winds and rains suddenly swept up the coast.

"It was terrible. The boat was hit by really strong wind, and shortly after it went down," survivor Charlotte Golunski told ANSA news agency.

Golunski, board director at Luminance, a company founded by Lynch, lost hold of her one-year-old daughter in the waves "for two seconds", before managing to grab her "while the sea raged".

"Lots of people were screaming" in the dark, said Golunski, who managed to get on a life raft.

Mast 'snapped'

Reportedly owned by Lynch's family, "Bayesian" was built by the Italian shipbuilding firm Perini Navi in 2008, boasting a 75-metre mast, the tallest aluminium sailing mast in the world, according to the Charter World website.

A photograph posted on social media Monday by the Baia Santa Nicolicchia bar in Porticello showed the yacht all lit up, its towering mast shining in the darkness, just a few hours before the storm hit.

A waterspout is a column that descends from a cloud to form a rotating mixture of wind and water over a body of water, often during severe thunderstorms.

"This is a large, luxurious superyacht that has founded quite quickly in a touristy, well-known sailing area off Sicily. It's pretty unprecedented," Matthew Schanck, from the Maritime Search and Rescue Council, told AFP.

"This is an extraordinary event. It's what I would class a black swan event," he said.

Karsten Borner, the captain of another yacht anchored nearby at the time of the storm, said there was a "very strong hurricane gust" and he had to battle to keep his vessel steady.

Borner saw the yacht's mast "bend and then snap", according to Italy's Corriere della Sera daily.

Italian authorities have opened a probe into the incident, while the UK's marine accident investigation branch sent four inspectors to Palermo.