At around 18:30 GMT Bourbon Dolphin finaly sank.
At the time she was no longer attached to the platform.
The deept is 1100 meter
This piece freom the BBC web site @http://news.bbc.co.uk/1/hi/scotland/north_east/6558439.stm
"Capsized rig support vessel sinks
Seven of the 15 crew members survived the tragedy
The oil rig support ship which capsized off Shetland, killing eight of the crew, may not be raised after it sank.
The Bourbon Dolphin overturned in the Atlantic on Thursday and coastguards said it sank at 2115 BST on Sunday.
Among those who lost their lives in the tragedy was a 14-year-old boy who was on work experience.
On Sunday, relatives of the dead crew members had gathered at a beach in Lerwick for a memorial service before flying over the upturned ship.
Three bodies have so far been recovered and five others are missing, presumed dead. It is thought their bodies may still be inside the boat.
Mr Hafsas said he could not feel happy about being rescued
The ship's operator, Bourbon Offshore, had hoped to tow the vessel back to shore.
Describing the ship as "very unstable", Shetland Coastguard watch manager Neil Cumming said: "It was released from a rig yesterday and slowly it began to sink."
It is now thought unlikely the Bourbon Dolphin will be raised from the seabed, about 3,500ft down.
Survivors of the capsize joined relatives of the victims on the Sands of Sound beach where a service was conducted in Norwegian.
One crew member, Egil Hafsas, described what happened when the boat overturned.
He said he was on deck when the ship lurched and started to list.
He ran into the accommodation part of the main deck, grabbed a life vest and shouted for everyone to leave.
Then he jumped into the water along with two young trainees just before the ship rolled over into the sea.
Bourbon Offshore released the names of the dead and missing crew members, who included 14-year-old David Remøy and his father Oddne Arve Remøy, 44, the ship's captain.
The others are Ronny Emblem, 25, Bjarte Grimstad, 37, Søren Kroer, 27, Frank Nygård, 42, Kjetil Rune Våge, 31, and Tor Karl Sandø, 54.
The police investigation has been handed over to a Norwegian government commission set up to look into the incident.
The Norwegian Marine Commission inquiry could report findings as early as the beginning of next week."