Divers have entered the sunken superyacht as they continue to search for the bodies of six missing people, but face “significant challenges” during the rescue operation.

British tech tycoon Mike Lynch and his 18-year-old daughter Hannah are among six missing after a luxury yacht sank in a tornado off the coast of Italy. One person has already been declared dead and Morgan Stanley International Bank chairman Jonathan Bloomer and Clifford Chance lawyer Chris Morvillo are also among those missing.

Nick Sloane, an engineer who led the salvage operation for the wrecked cruise ship Costa Concordia in 2013, says rescue divers looking for survivors have entered a “critical” 24 hours – with some possibly trapped in air pockets inside the ship, but that time is running out to save them if that is the case.

Marco Tilotta, a diver from Vigili del Fuoco di Palermo who is coordinating the search and rescue, said the teams have been diving continuously since 11.30pm last night.

He said they always hope to find people alive, but the conditions below the water are clearly “prohibitive”.

When asked about the conditions that caused the boat to sink, he said: “Of our entire career as divers, however, these are events that are clearly difficult to prevent and therefore truly unlikely and difficult to manage, so I don’t dare think of what the people who were there on board experienced.”

The British-flagged superyacht Bayesian is still largely intact on the seabed, but the 50m depth makes it difficult to access, and the time window divers have make searches is incredibly tight, according to another diver.

Among those diving are two cave divers, who will have experience navigating through tight areas.

‘We didn’t see it coming’: Superyacht latest

“They can stay underwater for a maximum of 12 minutes, two of which are needed to go up and down,” emergency responder Luca Cari told Italian daily Giornale Di Sicilia.

“So the real time to be able to carry out the search is 10 minutes per dive.”

Mr Tilotta told reporters: “We plan… to search centimetre by centimetre.”

The vessel was lying on its right side, Mr Tilotta said. Divers had not been able to determine whether the 72-metre-long mast had snapped somewhere along its length.

Divers have entered the lounge via a ladder, Mr Cari said, and are now trying to find the best access point to enter the rest of the yacht.

And Italian paper Il Messaggero said they had also been able to open a hole in the side.

Mr Cari explained that divers had identified a glass window of the Bayesian through which they could enter, though it had to be removed in order to gain access. The window is 3cm thick, making removal difficult.

From the outside it is impossible to see inside the yacht, further hampering the search.

The rescue team already searched the command bridge, which “is full of electrical cables”, but did not find anyone in the area.

“The spaces inside the sailing ship are very small and if you encounter an obstacle it is very complicated to move forward, just as it is very difficult to find alternative routes,” he added.

Hatches and doors left open overnight on the superyacht Bayesian may have caused it to sink in Italy, a sailing expert also said.

Sam Jefferson, editor of magazine Sailing Today, believes the vessel’s huge mast would have acted like a sail to pin the boat down, and is also likely to have contributed to the deadly event.

Mr Jefferson said “I would have said that the boat got hit very hard by the wind, it was pinned over on its side.

“I imagine all the doors were open because it was hot, so there were enough hatches and doors open that it filled with water very quickly and sank like that.”

Read more:
Everything we know about luxury vessel sunk by tornado
Lynch’s co-defendant dies before yacht sinking

Mr Lynch, known as the “British Bill Gates”, has been in the headlines in recent months over a high-profile fraud case.

In June, he was cleared of all charges by a US jury related to the sale of his software company Autonomy to Hewlett-Packard in 2011.

His wife, Angela Bacares, was among the 15 people already rescued.

Among others said to be missing are lawyer Christopher Morvillo, a Clifford Chance partner and Mr Lynch’s co-counsel in his US trial, Mr Morvillo’s wife, Morgan Stanley International chairman Jonathan Bloomer, who is also chair of UK insurer Hiscox, and his wife Judy.