A British explorer is thought to be among those missing (Picture: Getty)

A rescue mission is underway after a tourist submarine, carrying five people to the wreck of the Titanic went missing in the Atlantic Ocean.

Among those feared missing is British billionaire explorer Hamish Harding and renowned French diver Paul-Henri Nargeolet.

On Monday afternoon, Rear Adm John Mauger of the US Coast Guard said that the vessel had between 70-96 hours of oxygen left, meaning its a race against time to find the craft.

The submarine submerged at on Sunday morning, and its supprt vessel  the Canadian research icebreaker Polar Prince, lost contact with it an hour and 45 minutes later.

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A rescue mission is now underway