British tech magnate Mike Lynch and five others are missing, feared dead after their luxury yacht sank in a tornado off the Sicilian coast.

The luxury vessel – named the Bayesian – was moored half-a-mile off the coast of Porticello when it sank around 5am local time on Monday.

Rescue efforts are currently underway, with Vincenzo Zagarola of the Italian Coastguard telling PA news agency authorities believe the missing six people are likely to be trapped inside the boat.

“Of course, we do not exclude that they are not inside the boat, but we know the boat sank quickly,” he said.

“We suppose that the six people missing may not have had time to get out of the boat.”

The cruise was reportedly a celebration of Mr Lynch’s recent acquittal of fraud charges in the United States.

– Who is involved and why were they there?

Technology tycoon Mike Lynch and his 18-year-old daughter Hanna – who had recently finished her A-Levels and was bound for Oxford – remain missing.

Also unaccounted for are Jonathan Bloomer, chairman of Morgan Stanley and insurance company Hiscox, and his wife, Judy, a respected psychotherapist; as well as Chris Morvillo, a lawyer from Clifford Chance and part of the legal team representing Mr Lynch, and his wife, Neda, who reportedly runs a luxury jewellery line.

The body of a man was recovered near the yacht, believed to be that of chef Recaldo Thomas, a Canadian-Antiguan man working onboard.

Fifteen of the 22 people onboard – including Mr Lynch’s wife, Angela Bacares  – were rescued after escaping onto a lifeboat.

The Telegraph reported Mr Lynch had guests from the legal firm that represented him and his own company to join him on the voyage.

Among others rescued were Charlotte Golunkski and her one-year-old daughter Sophie. The brave mother kept her daughter alive by holding her over her head while she was in the water.

– How did the boat sink?

Italian authorities have reported bad stormy conditions that caused the yacht to sink, but investigations into the exact circumstances of the tragedy remain ongoing.

It is believed the luxury vessel may have been hit by a water spout, a rotating column of wind that forms over a body of water and is often likened to a tornado.

According to the US National Ocean Service, tornadic weather spouts have the “same characteristics” as a land tornado and are often accompanied by severe thunderstorms, “high winds and seas, large hail, and frequent dangerous lightning”.

– What search and rescue efforts are underway?

Vincenzo Zagarola of the Italian Coastguard said the six missing tourists were feared dead.

Asked about their likelihood of being alive, he said: “Never say never, but reasonably the answer should be not.”

Italy’s fire brigade Vigili del Fuoco said it developed a plan to enter the wreckage of Bayesian, which is resting on the seabed off the coast at a depth of 50 metres. It described the operation as “complex”, with divers limited to 12-minute underwater shifts.

Firefighter divers reached parts of the vessel through the gap, Giornale Di Sicilia reported on Tuesday, but are yet to make it to the cabins.

“If you manage to get inside, you understand there is a world of objects. So, getting inside and descending into the compartment below from the stairs that are narrow and going into all of the cabins is a really hard and difficult job,” fire department diver Marco Tilotta said per Reuters news agency, according to the BBC.

“We are not stopping. We have resources, manpower and means. Our goal is to find all the people who are missing, so that is our job,”

Dr Jean-Baptiste Souppez, a senior lecturer of mechanical, biomedical and design engineering at Aston University, said the next 24 hours are “crucial” to find survivors trapped inside the wreck.

“The speed at which the vessel sank (a few minutes, according to survivor and witness accounts) and the fact that it remains intact and on its side could favour the formation of small air pockets inside,” he said.

“This is obviously highly speculative and impossible to predict accurately.”

Rescuers could be looking for signs of life including banging noises at regular intervals.

– Who is Mike Lynch?

Mike Lynch, the British billionaire and tech entrepreneur, owes his fame and fortune to software firm Autonomy, which he sold to Hewlett-Packard for billions in 2011.

Hailing from Suffolk, he graduated with a PhD from the University of Cambridge. Mr Lynch is married to Angela Bacares, with whom he shares two daughters.

The father-of-two has a reported net worth valued at around  £852 million, according to the Independent.

His business ventures led him to once be dubbed “Britain’s Bill Gates” but also landed him in legal trouble.

Autonomy’s sale was wrapped in fraud claims, and he faced civil action in the UK before being extradited to the United States to face criminal charges.

In June, he was cleared of 15 fraud charges after allegations he inflated Autonomy’s worth.

– What do we know about the Bayesian?

The 56-metre sailing boat was launched by Italian shipbuilder Perini Navi in 2008, according to the company website.

It was once called the Salute, but was later renamed after Lynch’s PhD thesis on statistical theory by mathematician Thomas Bayes.

Media reports suggest the yacht’s owner is listed as Revtom Limited, a company owned by Mr Lynch’s wife.

– Who was Stephen Chamberlain and how is he connected to the situation?

Stephen Chamberlain was an associate of Mike Lynch and stood trial for fraud alongside him after Autonomy’s controversial sale.

Days before the yacht disaster, Mr Chamberlain died after being hit by a car while out jogging.

Mr Chamberlain, Autonomy’s former VP of Finance, was cleared of all charges by a San Francisco court in June.

Relatives of Mr Chamberlain said in a tribute released through police that he was a “much-loved husband, father, son, brother and friend”.

“He was an amazing individual whose only goal in life was to help others in any way possible,” his family said.