A Spanish diver who survived 60 hours in an underground air pocket has described how he began to hallucinate as his compressed air tank ran out.
Xisco Gracia became trapped in a cave in Mallorca on Saturday after his air tank malfunctioned.
His diving partner was forced to leave him behind to go in search of help.
But it took more than two days to reach the experienced speleologist and geographer, who was left sitting in the dark alone.
"I lost track of time. I thought it had been five days, too long, so I thought [my friend] could not get out and could not find me," Mr Gracia told Diario de Mallorca [in Spanish].
He added: "After so long breathing an air so charged with carbon dioxide, I sometimes saw some things, like lights or bubbles, and I thought [someone] had come to rescue me - but when they did not arrive, I was discouraged."
His colleague, with whom he had been examining the topography of the cave, had managed to leave the cave and find help - but rescue efforts were hampered by the visibility in the water, which was described as being "like cocoa".
However, the two divers were praised for doing the right thing.
Enrique Ballesteros, of the Underwater Activities Task Force of Barcelona, told news agency EFE: "They could have tried to stretch one [diver's] air, but surely that would have been suicide and both would have died."
Mr Gracia, in his 50s, an experienced diver and expert in his field, according to local media, survived by drinking from a thin pool of fresh water in the air bubble, which was about 40 metres below the surface until he was found, 900 metres from the entrance to the cave, at about midnight on Monday.
He was kept in hospital overnight, but appears to be uninjured and already feels he has "mentally recovered", according to Primicia Web [in Spanish].
The local Guardia Civil said they would review the event to see if any lessons could be learned.