Six are missing, including a man dubbed the British Bill Gates, after a luxury yacht sank off the Sicilian coast.
Fifteen escaped from the sinking vessel. The search for the missing continues.
The Italian coastguard said the yacht — the Bayesian — was anchored off the shore of port city Porticello, near the Sicilian capital Palermo, when it was hit by bad weather on Monday, local time.
Eyewitnesses said it vanished quickly beneath the waves shortly before dawn.
Managers of the sailing vessel Bayesian, Camper & Nicholsons, confirmed to the ABC that the Bayesian encountered severe weather and subsequently sank.
"Our priority is assisting with the ongoing search and providing all necessary support to the rescued passengers and crew," they said.
"The wind was very strong. Bad weather was expected, but not of this magnitude," a coastguard official told .
Sicily's civil protection agency head, Salvo Cocina, said a waterspout — a tornado over the water — could have struck the yacht.
"They were in the wrong place at the wrong time," Mr Cocina added.
Search crews, including divers, are continuing to search the wreckage, lying at a depth of 49 metres.
Sicilian prosecutors have also opened an investigation into the event.
Rescuers recover the body of one of the aboard the Bayesian. ()
There were 12 passengers and 10 crew members aboard the yacht.
Of the 22, one man is confirmed dead and another six are still missing.
Italian media said the dead man was the yacht's onboard chef.
Lawyer Chris Morvillo (left), entrepreneur Mike Lynch, and Morgan Stanley chairman Jonathan Bloomer are among the missing.
The still missing include:
Fifteen escaped from the sinking ship.
Eight have been hospitalised and others were taken to a nearby hotel.
Charlotte Golunski was among those rescued, recalling the harrowing moments she held her child Sofia above the waves. ()
Among those rescued were:
Mr Lynch, once hailed as Britain’s king of technology, was recently freed from a Silicon Valley lawsuit that tarnished his legacy.
The 59-year-old Cambridge-educated mathematician created Autonomy, a search engine that could pore through emails and other internal documents to help companies find vital information more quickly.
He received the OBE for his innovation in 2006.
He then sold the software to Hewlett-Packard (HP) for $US11 billion ($16 billion) in 2011, with Mr Lynch personally netting $US800 million.
Mike Lynch in 2019 leaving the High Court in London. ()
But the deal quickly turned sour after he was accused of forging the software's financial records to make the sale.
As part of a decades-long legal battle against HP, Mr Lynch was extradited to the UK on criminal fraud charges.
He steadfastly denied any wrongdoing, asserting that he was being made a scapegoat for HP's own bungling.
He was eventually cleared of all charges in June this year.
Following the San Francisco trial, Mr Lynch said he would return to the UK and do what he loved most: "[being with] my family and innovating in my field."
This picture shows the rescue operations off the Sicilian coast. ()
In a separate act of tragedy, Mr Lynch's co-defendant in the trial, Stephen Chamberlain, died on Monday, after a road accident left him critically injured.
Mr Chamberlain — Autonomy's former vice-president of finance alongside Mr Lynch — was hit by a car in Cambridgeshire on Saturday morning and had been placed on life support.
The luxury yacht is 56m long sailboat, with a 75m mast labelled as the tallest aluminium mast in the world.
The yacht, built in 2008 by the Italian firm Perini Navi, can accommodate up to 12 guests in six suites and a crew of 10, according to online specialist yacht sites.
Online charter sites listed it for rent for up to 195,000 euros ( $AU 321,000) a week.
This picture taken on Sunday shows the Bayesian (left) and the Duch sailboat Sir Robert Baden Powell anchored off the coast line. ()
The ship also won a string of awards for its design.
Ms Golunski said the yacht had travelled through the Aeolian Islands, Milazzo and Cefalù before sinking.
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