Mary Lee is a sixteen-foot, 3,500-pound great white shark tagged by oceanographers off the east coast of the US in 2012. The transmitter attached to her dorsal fin would be tracked by satellite when she surfaced. For the next five years Mary Lee’s movements were observed online by everyone from researchers to surfers, up and down the coast. She was tracked for nearly 40,000 miles until one day her signal stopped—probably because the battery on her transmitter expired...