Titanic tourist submersible: Rescuers scan ocean as clock ticks

US and Canadian search teams are racing against time to find a tourist submarine that went missing during a dive to the Titanic's wreck on Sunday.

Five people were onboard when contact with the small sub was lost about an hour and 45 minutes into its dive.

The rescue operation is continuing overnight in the mid-Atlantic but there has been no sign so far of the vessel.

Government agencies, both countries' navies and commercial deep-sea firms are all helping the rescue operation.

As of Monday afternoon, it was thought the crew members had roughly four days-worth of oxygen left. Among them is the British billionaire businessman and explorer Hamish Harding. read more