What we know about the sinking of Bayesian superyacht off Sicily

Six people are missing, including British tech tycoon Mike Lynch and a Morgan Stanley executive, one person is dead and there are 15 survivors following the sinking of a superyacht off the northern coast of Sicily.

Here is what we know about the Aug. 19 accident and what marine experts are saying about what might have happened.

VIOLENT STORM

The Bayesian, a British flagged 56-metre (184-feet) superyacht, sank in the dark shortly before 5 am (0300 GMT) off the port of Porticello, near Palermo, after being hit by a “violent storm,” the Italian coast guard said.

The coast guard said bad weather had been forecast, but added that it was more virulent than expected. Some locals spoke of a waterspout, or sea whirlwind, of exceptional force. “It was a strange thing,” fisherman Andrea Carini told Reuters. The Bayesian was at anchor, its sails down, when the tempest hit, with another yacht moored nearby.

THE OTHER BOAT

The nearby yacht, the 42-metre Sir Robert Baden Powell, remained anchored and weathered the storm after its captain turned on the engine to keep control of the vessel and avoid a collision with the Bayesian.

The captain, Karsten Borner, said he did not know if the crew of the Bayesian had managed to switch on its engines. “I don’t think they did things wrong, I think they were surprised by the power of the storm,” he told Reuters.

“I only know that they went flat with the mast on the water and that they sank in two minutes,” he said, adding that the storm was “very violent, very intense,” bringing in “a lot of water and I think a turning system like a tornado.”

SWIFT CAPSIZING

Andrea Ratti, a nautical design professor at Milan Polytechnic university, said a boat the size of the Bayesian could only sink so rapidly by taking in a huge amount of water. “One can make plausible assumptions that leave room for doubt” about what happened, he said, suggesting that one or more portholes, windows or other openings may have been broken or smashed open by the waterspout, letting in water.

There has also been media speculation that a major hatch might have been inadvertently left open.

However, an industry expert in Britain said it should have taken hours for the Bayesian to fill up with enough water to sink it, making its swift demise incomprehensible. “I don’t think the industry has ever faced anything like this. It’s a horror story,” he said, declining to be named.

Fire department diver Marco Tilotta told Il Messaggero daily the wreck was “apparently intact”, with “no gashes, no signs of impact”. However, only one half of the hull is visible to divers.

TALLEST MAST

The Bayesian was built in 2008 by Perini Navi, an Italian luxury yacht maker, and had won awards for its design. According to Perini, it featured the world’s tallest aluminium mast, measuring 72 metres.

Ratti said an unusually tall mast is not by itself an element of vulnerability in a storm. A second expert, structural engineer Filippo Mattioni, agreed, and also pointed to the possibility of “an open hatch” letting in water. Both experts were sceptical about a broken mast, which could have caused major damage smashing against the hull. “If the mast had been broken they wouldn’t have capsized,” captain Borner said.

RETRACTABLE KEEL

The Bayesian had a retractable keel – the fin-like structure under the hull that helps stabilise boats and acts as a counterweight to the mast. Both Ratti and Mattioni wondered if the yacht had been anchored with the keel up, reducing its depth under water from around 10 to 4 metres, making it less stable. Ratti said the boat might have started oscillating wildly, “like a pendulum”, under strong winds, putting exceptional strain on the mast. But even if this had led to its breaking, “this by itself is not enough to justify the sinking,” he said.

INVESTIGATION

Prosecutors in the nearby town of Termini Imerese have opened an investigation into the disaster. Their case is likely to take months to complete.