Wreck search, or more precisely the "investigation of underwater obstructions", is a special case of hydrographic surveying. In particular, the position and the shallowest depth of objects on the seabed are determined. Both information are usually displayed on the nautical chart.
Wreck search is the basis for the safety and efficiency of navigation. The information is mainly used for the safety of maritime traffic. Not only real wrecks are examined, but also all obstacles that pose a danger to navigation. Objects such as large stones, containers and others are also included. Wrecks that do not endanger surface navigation are also dangerous for fishing.
Various investigation methods are used for wreck searches. Sonars and echo sounders record the position and shape of the objects. Depth measurement is carried out with echosounders. As a rule, the investigation is supplemented by a diver who examines the obstacle more closely and determines the shallowest depth by measuring the compressed air.
Every year about 200 objects are examined, including about 40 new wrecks. Underwater obstructions are subject to constant change. The environmental conditions prevailing in the oceans influence the condition and stability of the objects.