A tourist submarine that focuses on exploring the Titanic shipwreck remains missing. The OceanGate Expeditions submersible has not been heard from for several days and has five people onboard, including Hamish Harding, a British billionaire. French diver Paul-Henri Nargeolet, Pakistani businessman Shahzada Dawood and his 19-year-old son Sulaiman Dawood are also on the submersible, named Titan. Stockton Rush, the founder of OceanGate Expeditions, may be the fifth person aboard but that had not been confirmed. It launched on Sunday June 18 and lost contact about an hour and 45 minutes later, reports say. The craft has a four-day emergency oxygen supply and time was running out as we went to press.