Rescuers frantically searching for the missing Titan submersible may take hope from a successful mission which saw a crew saved after spending 84 hours trapped underwater.
Titan lost contact with its mothership - the Polar Prince - about an hour and 45 minutes after it began diving down to see the Titanic wreckage - which sits on seabed 12,500ft (3,800m) below sea level - on Sunday.
