Grim hunt: an unidentified vessel sails close to the upturned hull of the Bourbon Dolphin in this videograb released by the coastguard
Teen feared among missing crew
A 15-year-old boy is feared to among five crewmen missing after the Bourbon Dolphin anchor handling tug support vessel capsized off the Shetland Islands yesterday, killing three people.
The search is continuing for five crewmen still unaccounted for. However, a coastguard spokeswoman says it would be a "miracle" if the five - thought to have been trapped inside the vessel - were found alive.
Ten crew members were found after the incident, which happened at about 5.20 pm local time on the Rosebank field, about 120 kilometres north-west of the Shetland Islands, where the vessel had been handling an anchor for the semi-submersible rig Transocean Rather.
Emergency services confirmed that three men had been found dead. The other seven rescued crew were airlifted to Gilbert Bain Hospital in Lerwick, Shetland.
The teenager is understood to be unaccounted for, along with his father.
Representatives from vessel owners Bourbon Norway and family members are expected to arrive in Shetland on a chartered flight from Norway today, the BBC said.
Searches by a coastguard helicopter for the missing crew resumed at first light this morning. Royal Navy divers continued to search throughout the night.
The spokeswoman for the coastguard said the operation is now being treated as a search and recovery operation.
"We are not really expecting to find survivors now," she told the BBC.
"It would be a miracle if they had survived all night in five degrees, freezing water. It's very sad."
Jim Sinclair, watch commander at Shetland coastguard, said four helicopters and between six and seven surface craft had been involved in the operation.
He said the divers were carrying out a survey and risk assessment of the ship using a remotely operated vessel.
Sinclair told the BBC: "It's a very complex and delicate operation as the vessel is actually upside down and stability is uncertain so they want to make sure of their own safety before they enter the hull.
"She is connected and that's one of the reasons that the Transocean Rather was down manned just in case the vessel came up towards the rig on the tide change and damaged it."
Grampian Police said they would begin an investigation into the incident.
The AHTS vessel, which is owned by Bourbon Norway, the Norwegian unit of French offshore services giant Bourbon Marine, is less than one year old, and has a crew of 15.
Bourbon Norway boss Trond Myklebust told the BBC: "There are divers at the scene and they have heat seeking cameras and there are also diving support vessels at the location."
He added: "The vessel is more or less brand new. It has been doing this operation since it was delivered.
"This is a common task and a common job in the whole area and it's absolutely incredible what has happened. We cannot understand it or believe it because this should not happen."
He said he could not speculate on what had caused the accident but said the vessel was carrying out an anchor handling operation with the rig and was connected to it.
The coastguard confirmed that the ship was still attached to Transocean Rather rig by an anchor chain.
As a result, non-essential staff have been removed to Shetland as a precaution.
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."
It is not known whether the missing crew members had been wearing survival suits or life jackets at the time of the incident.
All of the Bourbon Dolphin's crew are Norwegian nationals.