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An experienced boat captain whose vessel was anchored near Mike Lynch’s superyacht when it sank in a violent storm off the coast of Sicily on Monday said the stricken vessel appeared to have capsized because of its extremely tall mast.

“In my opinion, there is something wrong with the stability,” Dutch captain Karsten Börner told the FT about the sinking of the 540-ton Bayesian, which killed the British technology entrepreneur and six others, including Lynch’s daughter.

“With this extreme mast, the center of gravity is too high,” says Börner about the highest aluminum boat mast in the world.

He rejected an initial assessment by the Italian coast guard that Bayesian was “in the wrong place at the wrong time.” He said: “I was in the same place. I have two masts and they are 28 and 29 meters above deck, she has one, 73 meters above deck.”

From his own boat, Börner witnessed the sinking of the Bayesian in the violent storm before rescuing 15 survivors from the Lynch family yacht.

He said the wind was “tremendous, very strong,” estimating it reached force 12 on the Beaufort scale – hurricane force. “Tons of water came down. I’ve never experienced anything like it, it was a water tornado,” he added.

Börner, 69, who has 41 years of industry experience, said the survivors he rescued told him the Bayesian sank in less than two minutes.

Video footage from a surveillance camera on the shore shows the yacht with its illuminated mast tipping to the side in the wind before the rain obscures the image and the lights disappear.

Börner, who has seen the footage, is convinced that it shows a Bayesian capsizing within seconds.

Giovanni Costantino, CEO of the Italian Sea Group, which also owns the Perini Navi yacht yard, had previously told the FT that Bayesian was “designed for absolute stability” and could support the ultra-high mast.

He said the yacht’s crew had not properly followed safety precautions. ISG declined to comment on Börner’s conclusions.

Bayesian Captain James Cutfield has not yet commented publicly on the disaster, but has been questioned by investigators.

Börner said Bayesian’s crew told him they had “closed the ship,” contradicting the ISG’s claim that the yacht’s hatches were left open.

He also said that Cutfield, who was among 15 survivors rescued by Börner’s boat before dawn on Monday, “was fully involved in the rescue.”

Cutfield remained in Börner’s boat to continue the search for survivors and then transferred to the Coast Guard.

Sir Robert Baden Powell, the yacht captained by Börner, was anchored near Bayesian, in what was actually a relatively sheltered anchorage off Porticello, when the storm broke.

During the storm, Börner tried to keep his ship in position by starting the engine and pointing the bow into the wind.

Bayesian – which he used repeatedly to look for a possible collision during the storm – was behind them. “(They) did the same thing, I guess,” Börner said.

At one point, Börner’s passengers alerted him to what they thought was a “structure above the water” near them.

Borner said he turned around and saw a large triangle during a lightning strike. “I think they saw the ship capsize and when I turned around I saw the bow, then it went under,” he added.

An Italian official said a prosecutor investigating the sinking of the Bayesian is looking into the possible offense of “negligent shipwreck.”

If the UK-registered boat, designed by Ron Holland and built in 2008, did capsize, the so-called lifting keel could have been a cause.

According to ISG, Bayesian can withstand a tilt of up to 73 degrees without capsizing when a yacht’s keel is raised to enter shallow anchorages or harbors.

With the keel down – the safer position – she can lean up to 88 degrees, a nearly flat position with the mast on the water. It is not yet known whether the keel was up or down.

Börner said he has noticed the effects of global warming on Mediterranean weather in recent years.

“Now we have medicanes – hurricanes in the Mediterranean – that’s something new,” he said, adding that he had noticed an increasing trend in storms in the Mediterranean over the past five to 10 years.