People have sailed the waters of the Mediterranean Sea for thousands of years. Foley calls the Mediterranean Sea bottom “the biggest museum gallery in the world.” He is working with Greek archaeologists there to explore a massive wreck off the Greek island of Antikythera (An-tee-KITH-air-uh). The ship there sank more than 2,000 years ago. It carried many expensive objects, including statues, glass bowls, perfume jars, coins and jewelry.
Reaching the wreck is hard because it lies 55 meters (180 feet) below the water’s surface. That’s deep enough to fit an 11-story office building. Normally, even trained divers can only safely stay at that depth for a few minutes. But Foley and his team are using advanced equipment that gives divers enough time deep underwater to map and excavate the huge wreck.
Greek fishermen were diving for sea sponges when they found the wreck in 1900. Scuba had not yet been invented. The fishermen instead had one canvas diving suit that they traded between them. The air in the suit’s bronze helmet came through a pipe that ran up to the boat. The men managed to bring up some of the wreck’s cargo. The most amazing find was a machine known as the Antikythera Mechanism. Made of more than 30 bronze gears, it shows the phases of the moon and positions of five planets known to the ancient Greeks.
No one else tried to reach the Antikythera wreck until the 1970s, when Jacques Cousteau (ZHOCK koo-STO), the famous French oceanographer, dove there. His crew found more items, including coins and jewelry. But even with scuba gear (which Cousteau had helped to invent), they could only spend about 10 minutes at the wreck on each dive. Much of the ship’s cargo has never been raised from the deep. Foley and his colleagues want to bring up more of that cargo and figure out what kind of ship carried it. In 2014, they used cameras on an underwater robot to make a three-dimensional digital map of the site. It led divers to more goods buried in the sediment. Among their finds was a 2-meter (more than 6-foot) bronze spear. Work will continue at the site for the next five years.
Diving to the wreck is challenging because humans did not evolve to breathe underwater. The compressed air in scuba divers’ tanks contains a mix of mostly nitrogen and oxygen. When we inhale, our bodies use the oxygen to make energy. Our bodies don’t use nitrogen from air, so we exhale most of it, along with carbon dioxide and any unused oxygen. A tiny bit of the nitrogen dissolves into our blood-stream, but it does not have any effect.
But when a diver swims underwater, the water pushes down on their body. That extra pressure forces more nitrogen from their lungs into the bloodstream and tissues than would be absorbed at the surface. The longer a diver stays underwater and the deeper he goes, the more nitrogen his body absorbs.
When the diver rises to the surface, the pressure on his body decreases and the extra nitrogen dissolves out of his tissues. That process is called decompression. If divers ascend too quickly, the nitrogen can form bubbles in their tissues or bloodstream. This is known as decompre-ssion sickness. It can cause joint pain (also known as “the bends”) or harm the brain or spinal cord. Two Greek divers who explored the Antikythera wreck in 1900 became paralyzed from decompression sickness. Another died.
To spend more time underwater, divers at the Antikythera wreck today use special gas mixtures that do not cause decompression sickness. 
Until tomorrow: Working hard and working smart sometimes can be two different things. 

Dorothy Prats
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