The British-flagged luxury yacht The Bayesian capsized early Monday off the coast of southern Sicily with 22 people aboard.
Here's what is known about the 12 passengers and 10 crew members, believed to have hailed from Canada, France, Ireland, Myanmar, New Zealand, Sri Lanka, the UK and the United States.
British tech tycoon Mike Lynch and his 18-year-old daughter Hannah Lynch are among those unaccounted for, according to Italy's Civil Protection Agency.
Lynch, once dubbed the British "Bill Gates", founded software firm Autonomy in the 1990s but its $11 billion sale to Hewlett-Packard in 2011 saw him face fraud charges in the United States.
A jury in San Francisco acquitted the 59-year-old and a co-defendant of all charges in June.
It is understood he organised the yacht trip as a post-trial celebration for family, as well as some of his lawyers and employees.
His missing daughter was set to study English at Oxford University after finishing school this year, The Times reported.
Jonathan Bloomer, the 70-year-old British chairman of Morgan Stanley International, and his wife Judy, a charity trustee, are also among those missing, UK insurer Hiscox said Tuesday.
American lawyer Chris Morvillo -- a partner at the high-profile Clifford Chance law firm, who worked on Lynch's recent US fraud trial -- is also missing along with his wife Neda.
Confirming the pair were not accounted for in a statement Tuesday, a Clifford Chance spokesperson said: "We are in shock and deeply saddened by this tragic incident."
The body of one man was found in the sea a few hours after the disaster unfolded off Porticello, east of Palermo.
Officials have said he was the yacht's chef, with different media outlets naming him as either Ricardo or Recaldo Thomas.
He is reportedly Canadian-born, and had been living in Antigua.
Lynch's 57-year-old wife, Angela Bacares, who is also Hannah's mother, was among the survivors, officials have confirmed.
She was seen in a wheelchair after suffering abrasions on her feet, according to the Italian newspaper La Repubblica.
The paper reported she had been taken to a regional hospital, where she told doctors the boat began to tilt at around 4:00 am local time, waking Bacares and her husband.
She had then climbed up to the deck to assess the situation when the vessel suddenly started to capsize, the paper said.
Briton Charlotte Golunski, 35 -- a partner at Lynch's investment firm Invoke Capital who previously worked at Autonomy -- her partner James Emslie, and her one-year-old daughter also survived.
Golunski told La Repubblica they made it out alive because they were on deck when the yacht sank, describing in dramatic detail holding her baby above the surface of the sea to save her.
She said a lifeboat then inflated and 11 people eventually climbed in, with all three family members unharmed.
Ayla Ronald, 36, a London-based lawyer for Clifford Chance originally from New Zealand who also worked on Lynch's fraud case, "thankfully survived the incident", the law firm confirmed.
It noted her partner, believed to be named Matthew Fletcher, also made it out alive.
Her father Lin Ronald told various media outlets that she had texted him that they were "very shocked at the moment".
Other media reports have said another New Zealander, James Caulfield, 51, survived.
Meanwhile Irish citizen Sasha Murray, 29, injured her right foot in the tragedy, according to the Irish Times.
Frenchman Matthew Griffith, 22, is also said to have survived.
The boat's crew are believed to include Sri Lankans, as well as a citizen of Myanmar named as 39-year-old Myin Htun Kyaw, according to reports.
