A couple and their two teenage daughters are awaiting rescue from the south Atlantic today after their yacht hit an iceberg, the coastguard said.
The family, from Derbyshire, ran into trouble north-east of South Georgia after they hit a low-lying, mostly-submerged iceberg, known as a "growler".
Falmouth coastguard is helping the Falkland Island authorities to bring back the vessel, described as "stable" although it has taken on some water and has no engine power.
A coastguard spokesman said today: "What they've hit is a 'growler', where hardly anything is out of the water and the majority is submerged.
"It is very similar to what the Titanic hit. You can track them by radar or visual lookout, but you can't see them all."
The service was alerted to the family's predicament on Friday evening after their emergency radio beacon was activated.
Their position was pinpointed as 285 miles north-east of South Georgia, and the Falmouth team contacted the Falkland Islands.
Falmouth watch manager John Rossiter added: "The Falkland Island authorities have now spoken to the couple on their satellite phone.
"Their vessel is stable but it has taken some water and has no engine power.
"It seems that the yacht hit a low-lying iceberg in bad weather and broached.
"There were 50 knot winds from the west earlier on, but the weather is now improving.
"The warship HMS Clyde is 200 miles south of the yacht and is making its way towards the family."
The ship is due to arrive on scene at around 4pm today, and the family are expected to be taken to the Falklands. They are not believed to be short of food or water.
The Falkland Island authorities are co-ordinating the incident and are liaising with teams at Falmouth and Kinloss.
Mr Rossiter said: "We are ensuring that the Falklands have all the information that they need about the yacht and are liaising with shore contacts here in the UK."