The fish had gone to Hell, we all agreed. When we winched it back on deck, it had turned coal black and reeked of hydrogen sulfide, like rotten eggs. Demons might as well have been clinging to it.
This "fish" was actually a 2,000-pound (907 kilograms) iron weight that stabilized a sonar sled towed behind our 250-foot (76.2 meters) oceanographic research vessel, Northern Horizon. The sled had been scanning the sea bottom for solid targets that stood out from the bottom muck. After only 24 hours the weight was thoroughly corroded. Wise guys on the team promptly christened it Tetanus, Greek god of rust.
The Black Sea had a nasty reputation, even with the ancient Greeks. They once called it Axenos, "inhospitable," for the ferocity of its storms and the hostility of the tribes that lived around it. We were steaming off the north Turkish coast near the ancient seaport of Sinop, in the fifth year of research into the substance of the Black Sea, a great kidney-shaped pool about 700 miles (1,126 kilometers) long and 250 miles (402 kilometers) wide, a sort of little brother to the Mediterranean. Aboard was a skilled interdisciplinary team: robotics experts from Woods Hole Oceanographic Institution and my own Institute for Exploration; scientists from the University of Pennsylvania and the Institute of Nautical Archaeology at Texas A&M; and students from MIT and Columbia University. Journalists and a television team from the National Geographic Society, which has partly funded the project, competed for bunk space with other financial supporters and Turkish officials.
Tetanus's corroded condition notwithstanding, the sea surface glittered benignly in the early September sunlight, and porpoises cavorted at our bow. The markets of Istanbul had been silver with tubs of bonito, mackerel, and hamsi, the Black Sea anchovy. Clearly life inhabited the upper reaches of the Black Sea. What then made the water 600 feet (183 meters) below, where Tetanus had suffered, as hostile as the storms of Saturn?
We knew that the Black Sea, millennia ago, was a freshwater lake about two-thirds its present size and unconnected with the Mediterranean. It must have been an oasis in a dry region in the time we now call Neolithic, the late Stone Age. We also knew that melting glaciers had raised sea levels as the last ice age waned some 12,000 years ago and that the Mediterranean breached the Bosporus Valley to flow into the Black Sea Basin. The denser salt water filled the bottom of the basin, leaving a layer of lighter, brackish water on top. Since the Black Sea lacks the temperature differences that drive circulation in the world's oceans, oxygen from the atmosphere couldn't reach the sea bottom. Deadly hydrogen sulfide formed there, and life suffocated.
Toxicity was precisely why I wanted to explore those murky depths. Twenty-five years ago the late Willard Bascom, a pioneer of deep-sea exploration, postulated that the bottom of the Black Sea was rich in preserved shipwrecks because the anoxicity (lack of oxygen) meant an absence of wood borers such as teredo worms—mollusks that eat organic matter—and other marine life. Thus wood, canvas, cargoes such as grain and hides, and even human remains would theoretically be preserved.
Nobody had followed up on Bascom's theory until now. Leading nautical archaeologists, such as George Bass, were using scuba in shallow waters, maintaining that ancient trade routes followed coastlines, staying within sight of land. But surely there were captains bold enough to strike off across the unknown. They were businessmen after all, with a keen interest in saving time and money.