The search operation, which involves specialist divers aided by an underwater drone, continued until late yesterday and resumed at first light this morning, firefighters said.
The 56m British-flagged “Bayesian” was anchored with 10 crew and 12 passengers on board when it was struck by a waterspout – akin to a mini-tornado – before dawn on Monday.
One body was found in the hours after the sinking, believed to be the yacht’s chef, and 15 people were rescued.
But UK tech tycoon Mike Lynch and his teenage daughter Hannah, his lawyer Christopher Morvillo and his wife Neda, and Jonathan Bloomer, the chair of Morgan Stanley International, and his wife Judy remain missing.
Firefighters said yesterday evening that divers had entered the inside of the wreck, but that it was a “long and complex” operation.
The yacht is largely intact, resting on the seabed some 50m down.
Despite eyewitness testimonies that the 75m mast had snapped, reports today suggested that it too, survived the incident.
A coast guard official, captain Vincenzo Zagarola, had told Italian radio yesterday morning that it was “difficult to imagine” that the search would end well.
But experts noted that superyachts such as “Bayesian” were designed with watertight subdivisions.
“There are records of survivors found in such air pockets,” noted Dr Jean-Baptiste Souppez, a UK engineering expert and fellow of the Royal Institution of Naval Architects, in a commentary provided by the Science Media Centre.
He noted the case of Nigerian sailor Harrison Okene, who was rescued in 2013 after spending nearly three days trapped in an air pocket after his ship capsized in rough seas off the Nigerian coast.
But he added: “Whether air pockets formed on the Bayesian is simply impossible to predict.”
The passengers were guests of Lynch – an entrepreneur sometimes referred to as Britain’s Bill Gates – to celebrate his acquittal in a massive US fraud case.
The 59-year-old was acquitted on all charges in a San Francisco court in June after he was accused of an US$11 billion fraud linked to the sale of his software firm Autonomy to Hewlett-Packard.