National Geographic : 1976 Jun
There's glamour in finding treasure -and a lot of hard work in looking for it. Using a theodolite (left), salvors track a boat carrying a magnetometer, a device that indicates the presence of ferrous metals. False alarms are many, with or without the instrument; divers located muskets but also found fish traps and a World War II aircraft. Exploring the area where metals have been located, the Southwind, a former Mississippi River tug (above), trails a plume of sand as she blows craters in the seafloor; clustered pits, right, yielded so many coins that divers dubbed the place the "Bank of Spain." Another method, for deep re trieval: a water jet and hydraulic dredge (right) that removes mud.