The group of five Italian divers is believed to have died while exploring a cave at a depth of about 50 metres in Vaavu Atoll on Thursday, according to Italy's foreign ministry.
The recreational diving limit in the Maldives is 30 metres.
Maldives presidential spokesman Mohammed Hussain Shareef said that Mohamed Mahudhee, a member of the Maldivian National Defence Force, died of underwater decompression sickness after being transferred to a hospital in the capital.
"The death goes to show the difficulty of the mission," he said.
Earlier, Shareef said the searchers had prepared a plan based on their progress exploring the cave on Friday.
Mahudhee was part of the group that briefed Maldives President Mohamed Muizzu on the rescue plan when he visited the search site on Friday.
Rough weather has repeatedly hampered recovery efforts.
Italian Foreign Minister Antonio Tajani said everything possible would be done to bring the victims home.
His ministry stated it was co-ordinating with Divers Alert Network, a specialist diving organisation, to support recovery operations and the repatriation of the bodies.
The cause of the deaths remains under investigation.
The victims have been identified as Monica Montefalcone, an associate professor of ecology at the University of Genoa; her daughter, Giorgia Sommacal; marine biologist Federico Gualtieri; researcher Muriel Oddenino; and diving instructor Gianluca Benedetti, according to the Maldivian government.
Benedetti's body was recovered on Thursday.
Montefalcone and Oddenino were in the Maldives on an official scientific mission to monitor marine environments and study the effects of climate change on tropical biodiversity, the University of Genoa said in a statement on Friday.
However, the scuba diving activity during which the deadly accident occurred was not part of the planned research and was "undertaken privately," it said.
The statement also said the two other victims - student Sommacal and recent graduate Gualtieri - were not involved in the scientific mission.
Cave diving is a highly technical and dangerous activity that requires specialised training, equipment and strict safety protocols.
Risks increase sharply in environments where divers cannot head straight up and at depth, particularly when conditions are poor.
Experts say it is easy to become disoriented or lost inside caves, particularly as sediment clouds can sharply reduce visibility.
Diving at 50 metres also exceeds the maximum depth recommended for recreational divers by most major established scuba certifying agencies, with depths beyond 40 metres considered technical diving and requiring specialised training and equipment.
Shareef said Benedetti's body was found near the mouth of the cave and authorities believed the remaining four had entered the cave.
Two Italians, a deep-sea rescue expert and a cave diving expert, are expected to join the recovery effort, Shareef said.
Italian officials said about 20 other Italians on the same expedition aboard the vessel Duke of York were safe.
Italy's embassy in Colombo was providing assistance to those onboard and had contacted the Red Crescent, which offered to deploy volunteers to help provide psychological aid.
The Maldives tourism ministry said it has suspended the operating licence of the Duke of York pending an investigation.
The Italian foreign ministry said the cave is divided into three large chambers connected by narrow passages.
Recovery teams explored two of the three chambers on Friday but the search was limited due to considerations over oxygen and decompression.
On Saturday, they would explore the third chamber, the ministry added.
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