Hundreds of miles east of Florida, on a ship in the middle of the North Atlantic Ocean, Ryan Marr squinted at his computer as sonar data streamed in. A master’s student in maritime history at East Carolina University, Marr typically used sonar as a tool to locate shipwrecks and other underwater areas of potential ethnographic interest. This time, though, he was learning how to use sonar to map a key deepwater area southeast of Bermuda.