Maritime Archaeology: Methods, History, and Discoveries Underwater

Maritime archaeology (otherwise referred to as underwater archaeology or nautical archaeology) is the discipline of locating, surveying, and excavating historical sites underwater. Shipwrecks and crashed planes make up the majority of underwater historical sites (it has been estimated by pioneering maritime archaeologist George F. Bass [b. 1932] that there could be as many as three million worldwide), but submerged settlements are an important category as well.

Prior to the 1960s and 1970s, it was commonly assumed that conditions underwater prevented accurate surveying and that most objects would be severely eroded, diminishing the incentive to expend effort and resources on such projects. Early maritime archaeologists such as Bass and Peter Throckmorton (1928-90), however, adapted the techniques of treasure hunters to the work of locating and excavating historical sites. The main development was the use of SCUBA diving equipment to make long trips underwater viable.

Maritime archaeologists must work in adverse conditions on these dives: the environment is cold and dark (and often foggy due to disturbed sediment), and underwater currents can be strong and treacherous. Using normal scuba apparatus, divers must take brief trips down to the site (a few minutes at the deepest depths) to depths of 90 meters. Technological advances of the last thirty years have improved capacity underwater, however: the use of atmospheric diving suits (ADS) can permit human investigation at depths of as much as 700 meters. Remote operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) can allow for investigation by a pilot on the surface at depths of up to 6,000 meters.

The advantages of maritime archaeology make these challenges worthwhile. Due to environmental barriers, many underwater sites have never been looted or reused, remaining preserved as they were in the moments they were submerged. Unlike comparatively well- preserved sites on land, such as tombs and temples, submerged sites were not intended for posterity: a sunken ship is a snapshot of a moment in time of daily life as it was lived, and a sunken city is preserved in its last moments of ordinary activity. In addition, whereas objects may be severely eroded above the sediment line, those objects buried beneath the silt are often nearly as pristine as the day they sank.

Methods of locating and surveying archaeologically worthy sites are fundamentally the same on land and sea. Careful examination of historical accounts produces theories of where significant events may have taken place or edifices may have been. Instead of relying on visual searches as archaeologists do on land, maritime archaeologists benefit from sonar technology. By bouncing sound waves off the seabed, surveyors are able to discover the location and even the shape of objects at great distances below, and even discover objects buried beneath the sediment through a technique called sub-bottom profiling.

Although underwater archaeology was not seriously pursued until the latter half of the twentieth century, one of the earliest-known attempts to explore a site deep underwater was by Francesco De Marchi (1504-76). In 1535, he used a diving bell to explore the remains of the Roman Emperor Caligula’s pleasure barges lying 18 meters below at the bottom of Lake Nemi outside Rome. However, it wasn’t until the nineteenth century that extensive efforts to explore underwater sites captured significant interest.

In the early nineteenth century, fishermen discovered the wreck of the Mary Rose, the flagship of King Henry VIII’s fleet, sunk in 1545, off the coast of Portsmouth. Charles and John Deane, inventors of the diving helmet, used early versions of diving suits and bells to search and excavate the Mary Rose in 1840. With their innovations, they were able to recover objects as heavy as a cannon.

The first systematic attempts to survey and excavate a historical site were at the Cape Gelidonya shipwreck, headed by Peter Throckmorton in 1960, an amateur archaeologist and photojournalist. Using information gathered from local sponge divers, a trading ship dated to 1200 BCE was discovered in coastal waters off Turkey. It marked the first time modern archaeological methods of mapping and recovery were employed underwater. The Cape Gelidonya project demonstrated that surveying and excavation could take place underwater in a precise and scientifically rigorous manner.

Enhanced capacity to investigate underwater is a two-edged blade. Treasure hunters and salvagers are able to raid sites of historical value and disturb the condition of such sites. In 2001, the United Nations Educational, Scientific and Cultural Organization (UNESCO) adopted the Convention on the Protection of the Underwater Cultural Heritage, which creates standards of practice for protecting and investigating underwater sites. Fifty-five countries have enacted the convention into law, although many important nations are not signatories, such as the United States, China, and India.

Maritime archaeology has had significant achievements during its short existence. Examples include the exploration of what is believed to be Cleopatra’s quarters off the shore of classical Alexandria (submerged 1,600 years ago) in 1992; investigation of the sunken city of Port Royal (Jamaica) in 1981—a massive earthquake submerged the city in 1692 in a matter of minutes, capturing the city in a snapshot moment of its life; and confirmation of the legend of the sudden kamikaze (divine wind) said to have smashed two fleets sent by Kublai Khan to invade Japan in 1274 and 1281, when the remains of the fleet were discovered off Takashima Island in the 1980s.

FURTHER READING: Catsambis, Alexis, Ben Ford, and Donny L. Hamilton, eds. 2011. The Oxford Handbook of Maritime Archaeology. New York: Oxford University Press.

Delgado, James P 2004. Sea Hunter: In Search of Famous Shipwrecks. Vancouver: Douglas & McIntyre.

Green, Jeremy. 2004. Maritime Archaeology: A Technical Handbook. New York: Routledge.