Adrienne Vaughan, 45, the head of Bloomsbury publishing house’s US branch, suffered fatal injuries after being knocked overboard by the impact.

The crash occurred right off the Amalfi coast, a popular summer holiday destination in Italy’s southern Campania region.

The Italian skipper of the motorboat Vaughan was riding on “is being investigated for suspected manslaughter and causing a shipwreck”, Salerno chief prosecutor Giuseppe Borrelli said in a news conference.

Vaughan had been on the motorboat late on Thursday afternoon with her husband and two children, aged 12 and eight years old.

She had been sunbathing when the crash happened, Borrelli said. Her 12-year-old daughter was also thrown into the sea but was unharmed.

Vaughan’s husband was hospitalised for injuries sustained in the accident, Borrelli said, while the children were being looked after by their grandfather, who had flown in.

Investigators have spoken to the people on the chartered sailboat, the prosecutor said, although he did not confirm Italian media reports that it was a wedding party with US and German guests.

The skipper, who is also in hospital with what Italian media said were fractured ribs, was tested for alcohol and drugs but the results “aren’t necessarily significant”, Borrelli said.

Experts would determine whether any substance taken would have affected the skipper’s ability to pilot the boat, he added.

Italian media reported on Friday that traces of cocaine had been found in the skipper’s blood.

The captain of the chartered sailboat, Tony Gallo, told the Repubblica newspaper that “the motorboat made an inexplicable, almost kamikaze manoeuvre”.

“They were coming from the opposite direction when they suddenly turned 90 degrees, diving under my bow,” he reportedly said.