Police divers have resumed searching for six people believed trapped in the hull of a superyacht that sank in deep seas off Sicily, including a tech magnate who was celebrating his recent acquittal on fraud charges with the people who had defended him at trial.
The resting place of their sailboat is 50 metres underwater off Porticello - a depth that required special precautions that complicated the work: recovery crews said they were working in 12-minute shifts, a measure that slowed down their efforts to reach the cramped inside of the wreck.
The Bayesian, a 56-metre UK-flagged yacht, was moored about 1km offshore when a storm rolled in before 4am on Monday.
Civil protection officials said they believed the ship was struck by a tornado over the water, known as a waterspout, and sank quickly.
Grainy film from closed-circuit cameras from shore, broadcast on the website of the Giornale di Sicilia, showed the majestic, illuminated 75-metre mast of the Bayesian weathering the storm and then disappear over the course of a minute.
Fifteen of the 22 people aboard survived, including a mother who reported holding her one-year-old baby over the waves to save her.
One body has been recovered, identified by officials as the Antiguan-born on-board chef.
The rest of the 10-person crew survived, including the captain whom prosecutors reportedly sought to interview.
"It's a great, great tragedy," UK ambassador to Italy Edward Llewellyn said as he visited Porticello on Tuesday.
The United Kingdom sent four investigators to the scene, given the disaster involved a UK-flagged ship and UK citizens were among the missing.
Fire rescue officials have said the six other passengers will be considered missing until they are located in the wreckage.
They include the tycoon Mike Lynch, who was once hailed as the UK's king of technology and was cleared in June of fraud and conspiracy charges in a US federal trial related to Hewlett Packard’s $US11 billion ($A16 billion) takeover of his company Autonomy Corp.
Also unaccounted for are Christopher Morvillo, one of Lynch's lawyers, and Jonathan Bloomer, a chairman at Morgan Stanley International and the former head of the Autonomy audit committee who testified in Lynch’s defence.
Karsten Borner, the captain of the Sir Robert Baden Powell, which rescued the 15 survivors who managed to get into a lifeboat, said he was close enough to be able to see the Bayesian as the storm came in.
"A moment later, she was gone," he said.
"They said they went flat on the water and were sunk in two minutes," Borner added, quoting the survivors.
The rotating search teams, each made up of two specialised cave divers, worked on Tuesday to open up access points to get inside the wreck, which lies at a depth far beyond what most recreational divers are certified to reach.
They were using a remote-controlled underwater vehicle, or ROV, to help in the search.
The divers have not yet been able to access the below-deck cabins because they were blocked by furniture that had shifted during the violent storm.
Rescue crews said they assume the missing six are in those cabins because the storm struck when most would be sleeping but the teams have not verified their presence there through portholes.
Luca Cari, a spokesman for the rescue teams, said the search was proceeding much more slowly than another big shipwreck in Italy, the 2012 Costa Concordia cruise ship that flipped on its side off Tuscany's coast, because of the depth of the wreck and the limited space divers have to manoeuvre.
"That was much simpler. Here everything is more tight," he said.
The outing was intended at least in part as a celebration of Lynch's acquittal and a "looking forward to what was coming next," said Reid Weingarten, a US lawyer and a member of Lynch's defence team who was not on the yacht.
"A lot of people went, a lot of people were planning to go and then of course this happened," Weingarten said.
Some of the people who stood by Lynch throughout the ordeal were on board, including Morvillo, the lawyer, who Weingarten worked with and said "was like a brother".
Morvillo's wife Neda is also missing, according to his law firm Clifford Chance.
In an unrelated event, Lynch's co-defendant in the Autonomy trial who was also cleared, Stephen Chamberlain, was killed on Sunday when he was hit by a car while running in Cambridgeshire, England, Chamberlain's lawyer Gary Lincenberg said.
