In early August, blue crab fans took over Lewes, Delaware, for the Crab Pot Jamboree, where the biggest catch was learning how to avoid turning your crab pot into an underwater lost-and-found.

Under the leadership of Robert Rines, a lawyer trained in physics, the team pointed a sophisticated form of sonar, called side scan sonar, out into Loch Ness from a point near the shore.

Their main search tool was a deep-water, multi-beam, side-scan sonar, or ‘fish’, that was towed behind the ship at the end of some 4,000 to 6,000 m of cable. As the fish proceeded through the ...