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Stefan B. Williams

Professor, Australian Centre for Field Robotics, University of Sydney

An undated photo shows tourist submersible belongs to OceanGate descents at a sea. Search and rescue operations continue by US Coast Guard in Boston after a tourist submarine bound for the Titanic's wreckage site went missing off the southeastern coast of Canada. (Photo by Ocean Gate / Handout/Anadolu Agency via Getty Images)

Missing Titanic sub: What are submersibles, how do they communicate, and what may have gone wrong?

Stefan B. Williams