A diver died on Friday duringpreliminary operations to recover a superyachtbelonging to Mike Lynch, the British tech tycoon, off the coast of northern Sicily, local police said. The 56-metre-long (184ft) Bayesian was moored off the small port of Porticello, near Palermo, in August last year when it was probably hit by a downburst, a very strong downward wind, killing seven people, including Lynch and his daughter Hannah. The diving accident happened on Friday while the diver was underwater in Porticello, police said, adding that the precise cause of death was still unknown. Theattempt to lift the yacht off the seabedis expected later this month and should help shed light on how a supposedly unsinkable vessel disappeared into the sea. Italian news agencies reported that the diver was a 39-year-old Dutch national who worked for Hebo Maritiemservice, a Dutch specialist salvage company. Hebo was not immediately available for comment. The complex salvage mission involves a remote-controlled saw chopping through the 72m (237ft) mast of the Bayesian, which has been lying on its starboard side 50 metres below the seabed. Salvage workers will use an undersea drone with laser scanners to pinpoint the yacht and conduct checks to ensure it is not leaking the 18,000 litres of fuel still inside the vessel. The operation will also involve two barges. The first is a 55m-long (186ft) craft called Hebo Lift 2, which has a 700 square metre (840 square yard) deck with a crane, specialist diving equipment and a remotely operated underwater vehicle. The second, Hebo Lift 10, is one of Europe's largest floating cranes. Weighing 5,695 gross tons, it will lift the yacht out of the water using its 83m (274ft) crane. The 56m (183ft) Bayesian was built by Perini Navi, an Italian shipyard, in 2008. Last year, Giovanni Costantino, the chief executive and founder of its parent company, the Italian Sea Group,said the yacht was "unsinkable". He suggested that doors or hatches must have been left open and has threatened legal action after some experts suggested thehuge mast may have been a factor. Broaden your horizons with award-winning British journalism. Try The Telegraph free for 1 month with unlimited access to our award-winning website, exclusive app, money-saving offers and more.