A56-meter-long luxury sailboat, the Bayesian, with 22 people on board, sank at dawn on Monday off Porticello, near Palermo, after a tornado hit the area.
Coast guards rescued 15 passengers but seven others were reported missing, including one person whose body was recovered later on Monday morning after firefighter divers reached the boat located at a depth of 49 metres, half a mile from the coast.
One of the survivors is a one-year-old child who was taken to Palermo's paediatric hospital.
The passengers on board the British-flagged boat were mainly from Great Britain, in addition to one citizen of New Zealand, one of Sri Lanka, one Irish national and two passengers with dual British-French citizenship.
The boat sank while it was moored in the harbor of Porticello at Santa Flavia near Palermo.
Carabinieri police, the 118 emergency medical service and the civil protection are aiding survivors.
Port authorities are investigating the accident.
British tycoon Mike Lynch, 59, founder of the multinational computer company Autonomy, is among the six people missing in the sailing boat shipwreck off the coast of Sicily this morning, the UK media reported.
Called the 'British Bill Gates', Lynch had ended up at the centre of a high-profile fraud case and in June a US jury acquitted him of all charges relating to the sale of his software company to Hewlett-Packard in 2011.