One person has died and six are missing after a superyacht capsized off the Sicilian coast in the Mediterranean on Monday at about 5am (03:00 GMT) after it was hit by stormy weather caused by a “waterspout” – or mini tornado – according to Italian authorities.

The cruise had reportedly been undertaken to celebrate the acquittal of British tech tycoon Mike Lynch, who has been missing, in a fraud trial in the United States in June.

His co-defendant in the trial, Steve Chamberlain, who was also acquitted in June, was killed after being hit by a car on Saturday.

Here’s what is known so far about the yacht, those on board and who died or are missing.

Who was on the superyacht which sank?

According to the Italian coastguard, the 56-metre-long (184 feet) British-flagged yacht, called the Bayesian, was carrying 22 people, including 10 crew members.

One person has been confirmed dead after rescuers located a body on Monday at a depth of about 50 metres (164 feet), the AFP news agency reported. Officials have not yet given the name of the deceased but Italian media reported that he was the yacht’s chef.

AFP reported on Tuesday that divers had spotted a second body inside the sunk boat, quoting a source close to the search operation. Authorities have not confirmed it yet, though.

While not all the names of the six missing passengers have been made public officially, they are understood to include:

• Mike Lynch, 59, a British-Irish technology businessman who co-founded British tech company Autonomy in 1996 and was once likened to Microsoft founder Bill Gates; he earned a PhD from Cambridge University
• Hannah Lynch, 18, Mike’s daughter, who had just completed her final school exams and was due to begin a degree in English at the University of Oxford this September
• Jonathan Bloomer, the 70-year-old British chairman of Morgan Stanley bank and the Hiscox insurance company, was confirmed as missing by Hiscox CEO Aki Hussain
• Judy Bloomer, Jonathan’s wife, was also confirmed as missing by Hussain
• Chris Morvillo, from British international law firm Clifford Chance, was confirmed to be missing by Salvatore Cocina, head of the Civil Protection in Sicily

Fifteen people, including Lynch’s wife, Angela Bacares, were rescued. Among others rescued were Charlotte Golunski, 36, a board director at Luminance, a software startup founded by Lynch; her husband, James; and their one-year-old daughter, Sophie. Golunski is understood to have kept her daughter alive by holding her above her head while she was in the water.

All those rescued are in stable condition, although eight of them have been hospitalised, according to Italian news agency Adnkronos.

What do we know about the Bayesian?

Italian shipbuilder Perini Navi constructed the superyacht in 2008 and refitted it in 2020, according to the company’s website.

The yacht’s owner is listed as Revtom Limited, a firm solely owned by Lynch’s wife, Angela Bacares, according to company documents seen by the Reuters news agency.

It was formerly called Salute but was renamed Bayesian after Lynch’s PhD thesis and his software that earned him a fortune. Both of these were based on the statistical Bayesian theory, championed by mathematician Thomas Bayes.

Where was the Bayesian last seen and where was it going?

The Bayesian was last located on Sunday evening in the Tyrrhenian Sea, east of the harbour at Porticello, according to ship tracking websites Vessel Finder and Marine Traffic.

Porticello is a port city located near the Sicilian capital, Palermo.

The yacht had departed on August 14 from the Sicilian port of Milazzo. Its destination was reported to be the Italian city of Bagheria by the tracking websites.

Did a waterspout cause the yacht to sink?

Italian authorities reported that the stormy conditions that caused the yacht to sink were triggered by a waterspout.

A waterspout is a rotating column of whirling air and water mist – sometimes referred to as a mini tornado – according to the website of the US National Ocean Service.

The website adds that a tornadic waterspout is a tornado that forms over water or moves from land to water. They are similar to land tornadoes and can occur during thunderstorms.

Who is Stephen Chamberlain and how is he connected to this case?

Chamberlain, 52, was Lynch’s co-defendant in a fraud trial in San Francisco, which saw both men acquitted in June.

Chamberlain died in a hospital from injuries sustained when he was hit by a car while out running in Cambridgeshire, United Kingdom, on Saturday. His death was confirmed by his lawyer Gary Lincenberg in a statement on Monday.

The fraud case related to Hewlett Packard’s $11bn acquisition of Autonomy, the firm Lynch grew into the UK’s leading tech company before it spectacularly unravelled after being bought by HP in 2011.

Lynch was extradited to the US in May 2023 and he spent more than a year under house arrest before his acquittal. Chamberlain was the former vice president of finance at Autonomy.

The yacht trip was supposedly a celebration of Lynch’s acquittal.

What’s next for the search and rescue operation?

Specialist divers began a search anew for the six missing people on Tuesday. Three divers, equipped with oxygen cylinders, descended beneath the surface to examine the wreck.

They initially faced difficulty accessing the yacht’s chambers because they were constricted by furniture.

An investigation into the wreck has been opened by prosecutors in the nearby Sicilian town of Termini Imerese.

What have survivors and witnesses said about the incident?

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

She added that she had lost hold of her one-year-old daughter in the water for “two seconds”, but then managed to grab her and hold her up over the waves until a lifeboat inflated and they were both pulled to safety. She reported that people were screaming.

Karsten Borner, a captain of a nearby yacht who witnessed the sinking, said he had turned on the engine of his ship to prevent collision with the Bayesian. “We managed to keep the ship in position and after the storm was over, we noticed that the ship behind us was gone,” he told reporters.

Bloomer’s wife, Judy, is a trustee of the Eve Appeal, a UK-based gynaecological cancer research charity. Athena Lamnisos, the CEO of the Eve Appeal, was quoted by the BBC saying she was “deeply shocked to hear the news that our very dear friend and her husband Jonathan, are among those missing”.