Underwater archaeologists study the past through the submerged remains of vessels and their cargoes, or even those of ancient cities. While some shipwreck-hunters hope to find long-lost treasure, underwater archaeologists are more interested in what shipwrecks can tell them about life in the past. Clothing and equipment can give a valuable “snapshot” of life at the time the ship went down. Unfortunately, some shipwrecks, especially those that went down in shallow waters, have already been plundered by treasure-hunters over the centuries.

Finding a wreck

Finding a shipwreck can be a long and difficult task. Historical documents and charts are often the only source of information about the location of a sunken ship, and they are often inaccurate and vague. But once in the right area, research vessels can pinpoint the shipwreck exactly using detection equipment such as sonar—which locates objects using sound waves—and magnetometers, which can detect metal objects below several layers of sediment. Divers exploring the seabed can use metal detectors to find iron, bronze, or even silver or gold below the coral and sand.

Before moving any find, divers record its position using tape measures, label it and make sketches. They video the site, as well as taking photographs which can be put together by computers to create a map of the whole site. Finally, the finds can be taken to the surface. Small items are placed into baskets and lifted by air-filled balloons (lifting bags), but heavy metal objects such as cannons have to be winched up from the research vessel above.