Cave divers searching shipwreck
Giglio - Trained to explore underground pools and lakes in intensely cramped and dark conditions, divers from the speleologist unit of Italy's firefighting services are being deployed to search the wreck of the Costa Concordia.
One of them, Paolo Boschi, has just finished an early morning inspection of the cruise liner as it lies, half-sunk, near Giglio island off Italy's western coast.
"We sometimes drill small holes through the ship's walls and then insert a tube with a micro camera attached to the front," Boschi said. The purpose of this procedure is to detect possible obstacles, including piles of furniture and other debris that were dislodged when the ship began listing after it ran aground on January 13.
The ship is equipped with 1 500 cabins, five restaurants and 13 bars.
"All that material could collapse on top of us, so it's vital we know what lies behind a door before moving in," Boschi says.
"Imagine a concert-hall piano crashing down on you," he adds.
For their above-water work, the divers also carry mountain-climbing equipment, including ropes and harnesses used to scale the sides of the vessel, which from the shore can appear like multi-storey building toppled to one side.
Boschi, like is colleagues, is wearing a wetsuit reinforced with Kevlar - the same material used to make bullet-proof vests.
The divers, who are also trained to handle explosives, have on several occasions positioned micro depth charges to blast their way through the 290m long vessel.
They operate as two-men teams and take turns working shifts that last around 30 minutes.
It has been six days since the accident happened and progress has been slow.
Slight movements of the ship - several centimetres at most have been detected so far - have forced search efforts to be suspended for stretches lasting more than 12 hours.
"Any movement by the ship is dangerous because it could cause a collapse, which could squash us or leave us stranded," Boschi said.
He was speaking as a new search inside the ship - more specifically the submerged part of the fourth level - was about to begin.
But the exhausted Boschi will play no further part in the mission.
He comes from Pisa, and is about to catch a ferry back home to the Tuscan mainland after the group he was working with was relieved by another team of divers.
Hope of finding any more survivors in the Concordia's wreckage is fading fast. But there still remains the task of finding bodies - about 20 of the 4 200 people on board the ship have yet to be accounted for.
Italian officials have described the search operations as a "race against time" due to the need to start emptying the ships tanks of thousands of tons environmentally-hazardous fuel which, in the event of a spillage, would pollute the pristine waters around Giglio - one of the Mediterranean's largest nature sanctuaries.
Weather conditions were forecast to worsen towards the end of the week, increasing the risk that rough seas could cause the ship to shift further - an event that would make leakages from its tanks more likely, experts say.
The divers' search mission is likely to be halted when the fuel-removing process begins - something which according to the Concordia's owner, Costa Crociere, should start by "the end of the week".
Asked if this would provide enough time to complete the exploration of the vessel, Boschi replied: "I don't think so".