A top Italian firefighting diver has described the “particularly difficult” search and rescue mission after the sinking of a luxury yacht off the coast of Sicily.

Seven people died after the Bayesian sank in a storm near Porticello at about 5am local time on Monday, including British tech mogul Mike Lynch and his 18-year-old daughter Hannah.

Adverse weather conditions and the position of the shipwreck were among the problems faced during attempts to retrieve the bodies of six people on board, officials said on Saturday.

The yacht is now resting at a depth of about 50 metres.

Guiseppe Petrone, chief of the fire brigades’ divers’ section, said the operation was an “unusual kind of scenario” which had been made “particularly difficult” by obstacles preventing access to the ship and its cabins.

The diver told reporters, through a translation provided by BBC News: “The depth prevented us from staying very long under water.

“And of course there was all the obstacles to getting in the vessel and of course all the safety measures had to be properly observed – that is to say, not risking (the divers’) lives.

“So it was particularly difficult and it was very slow, very slow work, especially since it required lengthy periods to remove the obstacles to the cabins.

“And, as I’ve said, we did actually manage to retrieve all the bodies and observe all our standards.”

The Palermo fire brigade chief told reporters that specialised divers, some local and others called in from across the country, had to deal with “very little visibility due to the weather conditions”.

Bentivoglio Fiandra, translated into English by the BBC, said the operation involved 123 dives and some 70 people each day, including eight expert deep-sea divers.

He added that the six people who remained on board the yacht were in the “higher part” of the wreck, after trying to take “refuge in their cabins”.

Ambrogio Cartosio, head of the public prosecutor’s office of Termini Imerese, praised the “incredible courage and skill” of firefighters and divers who had helped the operation.

According to the BBC translation, he said: “It is a very grave tragedy and in order to reduce the dimensions of the tragedy, we have called upon the co-operation of the firefighters, firefighting divers, who have shown incredible courage and skill, who carried out a very difficult mission indeed and have allowed us to inspect properly the wreck for bodies.”