2 Raising the Mary Rose
Reports in 1836 that fisherman had snagged their nets on wreckage bolstered confidence that the Mary Rose was still intact on the seabed after more than 300 years. At the time, divers retrieved several of the guns, but salvage operations failed to raise the ship to the surface. In the 1960s, a team of professional divers were tasked with investigating Solent shipwrecks. They began an earnest search for the Mary Rose using the coordinates given by the 19th-century salvage team.
It is often impossible to locate buried objects such as the foundations of ancient buildings or shipwrecks, without using geophysical surveys that can investigate the upper few metres of the subsurface by looking for differences in density or physical properties. Seismic surveys are used to locate buried building foundations on land. However, the seabed is relatively unconsolidated compared with the land surface so instead, for potential archaeological sites underwater, the geophysical technique of choice is sonar.