Answer: An autonomous underwater vehicle.
The San Jose, a three-masted Spanish galleon ship with 62 guns, was sunk in 1708 while carrying gold, silver and emeralds worth billions of dollars. A victim of the British navy during the War of Spanish Succession, it was discovered on Nov. 27, 2015, off the coast of Cartagena, Colombia. The Woods Hole Oceanographic Institution (WHOI), which partnered with Maritime Archaeology Consultants (MAC), Switzerland AG and the Colombian government to look for the wreckage, recently obtained permission to release some of the details from the find.
WHOI’s autonomous underwater vehicle, called REMUS 6000, was instrumental in the discovery. “The REMUS 6000 was the ideal tool for the job, since it’s capable of conducting long-duration missions over wide areas,” said Mike Purcell, WHOI engineer and a leader on the expedition, in a news release. REMUS initially discovered the wreck using sonar technology. The search team then sent REMUS to take camera images from 30 feet above the ship, which rests at a depth of more than 600 meters. It was those images that allowed the researchers to officially identify it as the San Jose.