Three crewmen rescued from a capsized oil rig anchor handling tug in the Atlantic have died, while divers are continuing to search for five others.
A coastguard spokeswoman said it would be a "miracle" if the missing crew members were found alive.
Rescue teams said 10 of the Norwegian crew had been recovered following the incident at 1700 BST, about 75 miles west of the Shetland coast.
Seven are in hospital, but the ship's owners said three others had died.
Searches by a coastguard helicopter have been stood down until first light but Royal Navy divers are continuing to search throughout the night.
Norwegian-registered tug supply vessel
Max draught: 6.5m
Deadweight (max): 2,500 t
Gross/net tonnage: 2,974t/892t
Speed: 17.5 knots (trial)
Capacity: 35 personnel
The spokeswoman for the coastguard said the search and rescue operation would be changed to a search and recovery operation on Friday morning.
"We are not really expecting to find survivors now," she said.
"It would be a miracle if they had survived all night in five degrees, freezing water. It's very sad."
It is thought that the five missing people may be trapped in the hull of the upturned boat.
Grampian Police said they would begin an investigation into the incident once the search and rescue operation was completed.
The ship, which is less than one year old, had been working in the vicinity of the Rosebank oilfield with a crew of 15.
Six Royal Navy divers were flown to the boat from Faslane on the Clyde.
RAF spokesman Michael Mulford told the BBC: "You realise that these guys, if they have managed to find that bubble of air, if they've managed to find just somewhere to keep themselves alive, the divers will get to them.
"The rig and the ship, if you like, are self-supporting. And it is going to be a very nerve wracking two or three hours until we finally establish the fate of the last five."
'Search and recovery'
A Maritime and Coastguard Agency spokeswoman said: "Shetland Coastguard have now stood down the rescue helicopters.
"They will resume the search for the remaining five crewmen again at first light, however the search and rescue operation will be changed to a search and recovery operation.
Two helicopters have been involved in the search west of the Shetlands
"A naval diving unit has been flown to the Transocean Rather platform and divers will be assisting in the continuing search throughout the night."
Trond Myklebust, manager director of Bourbon Norway which owns the ship, said: "There are divers at the scene and they have heat seeking cameras and there are also diving support vessels at the location.
"It is still an ongoing operation."
Rig operator Transocean said the 99 crew members of the Transocean Rather had been accounted for.
"As a precautionary measure, Transocean has taken the decision to down-man the rig of any non-essential personnel," it said in a statement.
"Coastguard helicopters are assisting in the down-manning of the rig. There is no report of any damage to the Transocean Rather."
The Bourbon Dolphin had a number of roles in the North Sea, including anchor handling and towing, the installation of subsea construction blocks and operations involving remote vehicles.