Passengers could still be alive in air pockets inside the sunken superyacht. But it's a long shot and time is running out.

• Divers are searching for missing people from the sunken superyacht Bayesian near Porticello, Italy.
• An expert told Business Insider they're likely looking for air pockets in the vessel.
• But it's unlikely survivors will be found, the Italian coast guard said.

Divers are searching the sunken superyacht Bayesian for air pockets where survivors might be trapped, but experts and officials say the mission is hampered by dangers and limited time.

The search and rescue operation for the six people missing from the Bayesian is continuing, after it sank in a sudden storm while anchored off the Italian port of Porticello early Monday.

Among the missing is British tech billionaire Mike Lynch . One person has been found dead and 15 were rescued from the vessel.

Matthew Schanck, chairman of the UK's Maritime Search and Rescue Council, told Business Insider that with around 36 hours having passed since the sinking, it appeared likely the missing are still on the vessel.

He added that relatively calm conditions in the hours after the storm passed and weak sea currents meant they'd likely have been found by now if they were on the sea's surface.

Schanck said search and rescue team divers will search the vessel "to see if they can see any casualties through windows or anything like that. They'll assess the structure of the vessel. Are there any air pockets, you know? Is there any noise or any signs of life, and that will factor into their decision-making."

Nick Sloane, who worked on the Costa Concordia salvage operation, told Sky News rescue time is running out to find survivors.

"They've got a very small window of time to try to find people stuck inside with hopefully an air pocket, and they could be rescued," he said.

"If the yacht is on its side, it might have more air pockets than if it's upright. She's got quite a large keel, and that will deflect and put her on her side, I'm sure," he added.

Schanck added that search and rescue leaders would weigh the risk versus the potential for finding survivors in deciding whether to send teams on highly dangerous dives into the sunken vessel.

"If you heard banging from inside you'd be able to take more risks to save a life. But if all the information is pointing towards the fact actually there's no evidence of air pockets, you've scoured the surface, and we think the casualties are in there, then it'd be very difficult for them justify divers entering the vessel to go and recover casualties," he said.

Vincenzo Zagarola, a spokesman for the Italian Coast Guard, told the PA news agency that the missing would unlikely be found alive.

"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."

When asked if there was any hope of finding the missing alive, he reportedly said, "Never say never, but reasonably, the answer should be no."

Schanck said there's no strict timeline for assessing when a search and rescue operation should be called off; it's a call made by team leaders based on the evidence available.

Lynch was among the UK's best-known tech entrepreneurs. In 2011, he sold his company Autonomy to Hewlett-Packard for $11 billion.

However, the deal led to a drawn-out legal battle, which resulted in Lynch's acquittal on fraud charges in the US in June.

His daughter, Hannah Lynch, is among the missing, while his wife, Angela Bacares, is among the survivors.