A series of "indescribable, unreasonable errors" by the crew led to the shipwreck in which British tech entrepreneur Mike Lynch and six others died earlier this week, the yacht manufacturer's CEO says.

The British-flagged Bayesian, a 56-metre-long (184-foot) superyacht with 22 people aboard – 12 passengers and 10 crew – capsized and sank within minutes of being hit by a pre-dawn storm while anchored off the coast of northern Sicily.

"The boat suffered a series of indescribable, unreasonable errors," Giovanni Costantino said.

"The impossible happened on that boat ... but it went down because it took on water. From where, the investigators will tell."

Costantino helms The Italian Sea Group, which includes Perini Navi, the Italian high-end yacht maker that built the Bayesian in 2008. The vessel has been refitted twice, last in 2020, but not by Perini.

The CEO ruled out any design or construction errors, which he called unlikely after 16 years of trouble-free navigation, including in more severe weather than when it sank.

He blamed the Bayesian's crew for the "incredible mistake" of not being prepared for the storm, which had been announced in shipping forecasts.

"This is the mistake that cries out for vengeance," he said.

Costantino said passengers should have been summoned out of their cabins and assembled at a point of safety while the boat was being prepared for the storm by pulling up the anchor, closing doors and hatches, lowering the keel to increase stability and other measures.

An Italian coast guard vessel conducts search operations where a luxury yacht sank, off the coast of Sicily. – Reuters

Six out of 12 passengers died in the shipwreck, and five bodies were found inside the wreck. Emergency services are still trying to locate the body of the last missing person, Lynch's daughter Hannah.

Had correct procedures been followed, all passengers would have gone back to sleep after one hour "and the next morning they would have happily resumed their wonderful cruise," Costantino said.

Another yacht anchored near the Bayesian escaped unharmed.

The captain of the sunken yacht and other crew members have not commented publicly on the disaster, while Italian prosecutors investigating it are due to hold a press conference on Saturday.