Finding a sunken shipwreck is not an easy or quick endeavor, so continue reading to learn what’s involved in a successful search. While several thousand sunken shipwrecks rest in U.S. waters, the vessels may be in pieces or covered under layers of sand. Also, they may be in very deep water that is inaccessible to divers or even too deep to find with remote sensors. Sometimes, however, explorers get lucky and find what they are looking for.
If we plan well, we may get lucky! Join us as we begin to explore our mystery target shipwreck during the summer of 2011.”
What's Involved –
To identify a target shipwreck, Voyage to Discovery archeologists have begun researching potential historic shipwrecks important to African-American maritime history, by investigating themes that relate to African-Americans at sea, and looking for ships and possible shipwrecks that can be found on this website. This initial research has lead archeologists to a target ship, allowing them to conduct more in-depth research in an attempt to determine where the ship may have sunk and whether it might be accessible.
Exploration – Archaeologists have several tools they use when searching for a shipwreck. Sonar is the main tool. A sonar sensor is a long, streamlined device with fins to stabilize it as it is dragged through the water by a boat or ship. The sonar shoots sound waves down to the seabed and receives the reflected sound when the waves hit solid objects. This is similar to the “echo-location” used by bats and dolphins. Because the sensor shoots and receives the sound from its sides, it is called “side scan sonar.” Computers turn the reflections into pictures of the objects that reflect the sound. There are also other types of sonar that the scientists use.
Archaeologists may also use a metal detector called a magnetometer to search for wrecks. Magnetometers can detect metal objects such as nails, cannon and many other things that were used on old ships. They are especially helpful when a ship is buried under sand and cannot be seen by sonar. Since the magnetometer does not produce images like sonar, archaeologists sometimes use both tools together when looking for shipwrecks. When scientists locate a target, they don’t immediately stop to look at it. Usually, they survey a wide area and keep working until the survey is complete. Then they begin the inspection phase.
Other, new technologies, including AUVs, or Automated Underwater Vehicles, are being developed that will also help archaeologists in the future. AUVs, which look like torpedoes, carry remote sensing equipment that can be programmed to search an area without needing to surface. AUVs are faster and less expensive than using a ship or boat to tow a mag and sonar.
Discovery – Once potential targets have been found, archaeologists must inspect them to see what they are and whether any of them are the shipwreck for which they are looking. If the targets are in shallow water, the team may even send divers down for a closer look.
When the sonar or magnetometer finds a target, the scientists always record the latitude and longitude of the locations so they know where to go back and search. Divers use Self Contained Underwater Breathing Apparatus or SCUBA to breath underwater. The divers form teams and swim in patterns to try to locate the targets. Sometimes they get lucky and find the shipwreck; sometimes it may turn out to be just a piece of junk or a boat-shaped rock; and sometimes they don’t find anything.
If the target is too deep to easily dive, the team may decide to use a Remote Underwater Vehicle (ROV). These are unmanned submarines that are linked to a ship by a group of cables. Operated from aboard the ship, the ROV may be equipped with sensitive cameras and powerful lights so that scientists can watch what the craft finds on TV monitors. This is how the remains of the steamer Portland were found in over 400 feet of water.
Archaeological Documentation – Once the shipwreck has been discovered, archaeological documentation work begins. Archaeologists take many pictures and measurements to map the site, as they must make sure they have the ship they are looking for and not making a mistake! On old wooden ships, the scientists are looking for objects that may contain the ship’s name, like a bell. Such a special artifact is not always present, so archaeologists also look for artifacts that might suggest the approximate time period during which the ship sailed and sank.
If enough of the wooden hull is intact, scientists might be able to compare measurements with what is historically known about the ship’s size. If the shipwreck site is within reach by divers, it is documented by hand with tape measures, cameras and special slates on which divers can write underwater. If the site is too deep for divers, then the scientists may use ROVs to do the work. ROVs may employ high-resolution cameras that look straight down and take multiple pictures that can later be put together to make a photomosaic, a series of overlapping photographs compiled into a single large image. ROVs are very useful in deep water where it is too dark to see the entire wreck. Since each photograph is taken with a powerful underwater light, the whole wreck appears as if in daylight.
Education – Since shipwreck expeditions often are undertaken with public money (i.e., government funding), archaeologists always try to include an educational component to help share the project with as many people as possible. For example, recovered artifacts can be included in museum exhibits. Sometimes a traveling exhibit is created to bring the excitement and insights of underwater discovery to national and international audiences. The Henrietta Marie’s slave ship exhibit has been on tour since 1995.
NOAA’s Office of National Marine Sanctuaries helps to host many educational programs such as archaeological dive trainings and Youth Education Summits with the National Association of Black Scuba Divers. These programs have enabled African American students to explore and help preserve shipwrecks in the Nation’s National Marine Sanctuaries.
These projects also make good use of the World Wide Web. A project may have its own website (just like Voyage to Discovery)! Sometimes a project may send the video taken by the ROV straight to the Internet for the public to watch. The Office of National Marine Sanctuaries’ Maritime Heritage Program uses the “OceansLive” marine science portal site to broadcast many of its projects as they happen. Watch one of the expeditions from earlier this summer, from the Montana shipwreck 60 feet below the surface of Lake Huron in the Thunder Bay National Marine Sanctuary!