MALE, Maldives — International cave diving experts have arrived in the Maldives to take over the perilous recovery operation for four missing Italian tourists, a day after a local military rescue diver died attempting to reach them inside a treacherous underwater cave system.

The five Italians are believed to have perished on Thursday while exploring the Vaavu Atoll. So far, only the body of diving instructor Gianluca Benedetti has been recovered near the entrance. Authorities believe the remaining four are trapped deep within the labyrinthine caves.

British cave rescue expert John Volanthen told CNN the operation faces “fatal” challenges. Extreme depths of up to 60 meters (nearly 200 feet), suffocatingly narrow passages, and near-zero visibility make the underwater terrain incredibly hostile.

Volanthen emphasized that diving at such extreme depths drastically increases the risk of nitrogen narcosis—a condition that impairs judgment, causes hallucinations, and triggers panic. Combined with thick silt on the cave floor and a complex zigzag layout, navigation is nearly impossible, even for elite professionals.

The missing individuals—identified as ecology associate professor Monica Montefalcone, her daughter Giorgia Sommacal, and researchers Muriel Oddenino and Federico Gualtieri—were all affiliated with the University of Genoa in Italy. Despite being experienced divers, officials noted they were using standard recreational gear rather than the specialized technical equipment strictly required for deep cave diving.

The group had embarked on the dive from the vessel Duke of York. Albatros, the agency marketing the tour, clarified they do not own the boat nor directly employ the local crew.

High-level communications are ongoing between Rome and Malé. An Italian envoy arrived in the capital on Friday to monitor the coast guard’s efforts firsthand. Italian Foreign Minister Antonio Tajani pledged that both nations will utilize all available resources to bring the victims home.