Race to save those missing in sunken superyacht off Sicily, but survival 'improbable'

LONDON and ROME -- Rescue teams are facing a “very hard” operation to find those still missing following the sinking of a superyacht off the coast of Sicily on Monday, a spokesperson for the onsite fire brigade teams has told ABC News.

Luca Cari said that the rescue operation for the six people still missing from the U.K.-flagged Bayesian yacht is ongoing as of Wednesday morning. The vessel was lost early on Monday in stormy weather around half a mile from the fishing village of Porticello, close to the city of Palermo.

Fifteen people have so far been rescued and one body has been recovered.

“For us, it remains a rescue operation,” Cari told ABC News when asked if emergency services were transitioning to a recovery operation.

Asked if there was any hope that the missing may be surviving thanks to air pockets inside the sunk vessel, Cari responded: “One can never exclude anything but it seems rather improbable.”

Cari said that 12 of the 18 divers leading rescue efforts on Wednesday are specialized cave divers who have extensive experience working inside caves.

Divers have been operating inside the yacht for two days, he added. “But the job is very hard because there are large obstacles and [we] have to work in very narrow spaces.”

“It’s a long process and we can only operate in short spells,” Cari added. Divers have to be rotated constantly, with each only able to stay underwater for around 12 minutes, he said.

Two Americans -- Christopher and Neda Morvillo -- are among the six people still missing, ABC News confirmed on Tuesday.

Christopher Morvillo is a partner at law firm Clifford Chance and represented the yacht’s owner -- British tech tycoon Mike Lynch -- in his recent fraud case brought by Hewlett Packard. He is a former assistant United States attorney for the Southern District of New York.

Lynch and his 18-year-old daughter Hannah are believed to also be among the missing.

ABC News' Joe Simonetti contributed to this report.