When the object of your search is under sand, beneath nine to 20 feet of water and scattered across hundreds of square miles, you need help. Michael Faught selected remote-sensing survey instruments used to find sunken ships to hunt for prehistoric artifacts. He called upon two kinds of sonar to locate the type of terrain where Florida's earliest inhabitants lived: flatlands near a source of freshwater.

A sub-bottom profiler is a sonar device that transmits high-pitched sounds capable of penetrating and reconstructing sediments at great depths. It can detect the presence of bedrock and identify the filled channels of drainage systems beneath the ocean floor. Researchers with the PaleoAucilla Prehistory Project use it to pinpoint springs, sinkholes and ancient river channels (Figure 1).

A second tool used to create images of submerged geologic features is side-scan sonar. This device sends sound waves in a bilateral angular pattern to the ocean's bottom. Each pulse of sound "sees" a 100-200 foot-wide swath of the ocean floor below and to the sides. The result is an image of the sea bottom with distinguishable features such as rock outcroppings (Figure 2), which could have served as a source of flint from which tools were made.

After sonar pictures of the terrain are studied, divers go in and visually inspect specific targets for geological features such as rocky outcrops, limestone rock fields and sediment beds. Faught and graduate students then sample the ocean floor by hand fanning for artifacts and to collect sediment samples. Information gathered from these inspections is used to determine whether more time should be devoted to the site.

If any artifacts are found, the location is designated as an "encounter". When 10 or more artifacts are found the site is given a state designation officially recording it with the Florida Bureau of Archaeological Research. —J.C.