An Australian diver seeking to recover the remains of a fellow explorer from a deep underwater cave in South Africa is missing, presumed dead.
Dave Shaw failed to return to the surface in Bushman's Cave, Northern Cape province, after attempting the descent to 271 metres (894 feet).
He had been trying to recover the skeleton of a South African diver, Deon Dreyer, who died in the cave in 1994.
Bushman's Cave is the third-deepest known freshwater hollow in the world.
Shaw, one of eight international divers involved in the operation on Saturday, had asked his colleagues beforehand not to try to retrieve his own body in the event of an accident.
The 50-year-old airline pilot's mission had been to make the deepest dive of the team, going to the bottom for a few minutes during which he would place Dreyer's remains in a body bag.
Concern was raised when he failed to appear at an agreed decompression stop 220 metres underwater.
"He is still down at the bottom and presumed dead," said Ernst Strydom, national coordinator for police divers.
"There's no chance someone can stay alive at that depth for that long."
Shaw had spotted Dreyer's skeleton during a dive into the cave on 28 October and had promised the dead man's family he would bring back his remains.
Deon Dreyer, a South African, blacked out during his dive in Bushman's Cave in 1994, at the age of 20.