More than 40 years ago, a Turkish sponge diver named Mehmet Çakir caused a stir among Anatolian archaeologists when he showed them sketches of objects that he had seen lying 150 feet deep on the seafloor off the coast of Kas, in southwestern Turkey. He described them as "metal biscuits with ears," but experts immediately recognized them as a type of metal bar known as an oxhide ingot that was commonly traded during the Bronze Age, 3,500 years ago.Authorities immediately began to search for the site, and soon came across the artifacts that Çakir had spotted not far offshore of...