A submersible watercraft with five people on board has been missing since Sunday after setting out to explore the site of the Titanic shipwreck in the North Atlantic. The vessel is thought to be equipped with only a few days’ worth of oxygen. An international team including the U.S. and Canadian Coast Guards, commercial vessels and aircraft have been involved in the search. Here’s what we know. #titanic #titanicsubmarine #oceangateexpeditions