Security camera footage showing the moments before a tornado sank a luxury yacht off the coast of Sicily has emerged, as rescue workers face tough conditions in the ongoing search for six missing people.

The black-and-white footage appears to show the British-flagged yacht, called the “Bayesian,” being battered by a violent storm on Monday. As rain lashes down on the port, the grainy video shows the boat rocking violently from side to side before capsizing.

The vessel sank early Monday – killing at least one of 22 people on board – after its mast, one of the world’s tallest, broke in half during the storm. Fifteen people have been rescued.

The body that was recovered from the vessel was identified as the onboard chef Ricardo Thomas, an Antiguan citizen, Reuters reported.

Among the missing is British tech tycoon Mike Lynch, Morgan Stanley International director Jonathan Bloomer, and Chris Movillo, a prominent American lawyer, according to Sicily’s Civil Protection.

Lynch’s 18-year-old daughter was also named missing. His wife, Angela Barcares, survived. Speaking to the Italian daily La Repubblica while sitting in a wheelchair in a Sicilian hospital, Bacares said she was woken at 4 a.m. local time as the boat tilted.

She said she and her husband were initially not concerned, but became worried when the windows of the yacht shattered.

The yacht sank after a small waterspout – a type of tornado – spun over the Mediterranean island, likely capsizing the boat, which was anchored about a half a mile from the port of Porticello. Eyewitnesses described furious gales and hurricane winds that left a mountain of debris near the pier.

One witness, the owner of a villa looking out to where the Bayesian was anchored, said that after news of the sinking yacht emerged, he watched back his CCTV footage, where the boat could be seen sinking.

“In just 60 seconds, you can see the ship disappear,” he told Italian outlet ANSA. “You can see clearly what’s happening. There was nothing that could be done for the vessel. It disappeared in a very short time.”

Emergency crews resumed their search for missing people on Wednesday, with an underwater and surface operation ongoing. Italy’s fire brigade have warned that divers only have up to 12 minutes at the wreck site – thought to be around 50 meters underwater (approximately 150 feet) – before having to resurface.

Divers were able to access the inside of the wreck on Tuesday, the brigade said, including some of the rooms under the yacht’s control bridge. But the operations are “complex” due to numerous obstacles and narrow passages inside the ship, they said, adding that Wednesday’s operation would attempt to open some of those passages.

Three days on from the wreck, investigators are still at a loss as to how the ship sank so quickly. Matthew Schanck, chair of the Maritime Search and Rescue Council, said Tuesday that such events are exceedingly rare.

“Looking at the extreme weather, if it was a water spout, which it appears to be, it’s what I would class as a black swan event,” he said, referring to a rare, unpredictable occurence. “Even outside of the maritime industry, all industries struggle with the black swan events,” he added.

And while Sicily isn’t “renowned” for tornadoes or water spouts, “there is a risk” they can happen – just not every day, Schanck said.

“I think it’s important to see what comes out that may suggest changes to vessel construction, vessel stability, potentially,” he said, stressing that shipbuilding regulations “are all designed with safety in mind.”