The Coast Guard’s Marine Board of Investigation began two weeks of testimony from former employees of OceanGate, the company that operated the Titan submersible, with investigators outlining multiple concerns about the vessel before its mission started. The submersible plunged thousands of feet below the North Atlantic Ocean in search of the Titanic wreck site when it imploded, killing all five on board. NBC News' Tom Costello has more.

Sept. 16, 2024.