Meg: Origins

In 1874, the research vessel HMS Challenger dredges gigantic fossilized shark teeth from the deepest part of the Mariana Trench, demonstrating the existence of a huge shark species believed extinct. In contemporary time, a research vessel sends a Deep Submergence Vehicle to prospect the same area, but it is attacked by what the pilot believes to be one of those giant sharks, killing the two scientist passengers. His superiors, however, refuse to believe him and blame the incident on error by the pilot, who was overly fatigued from being pressured into making too many dives in too short a time, but had been falsely given the OK to make this additional dive on orders from the captain; a fact which is not mentioned in the official record, which lays the entire blame on the pilot.