Archaeology

Ground penetrating radar can be used to map buried artefacts, such as graves, mortuaries, wreck sites, and other shallowly buried archaological sites.
Ground magnetometric surveys can be used for detecting buried ferrous metals, useful in surveying shipwrecks, modern battlefields strewn with metal debris, and even subtle disturbances such as large-scale ancient ruins.
Sonar systems can be used to detect shipwrecks.