A Bathymetric chart is a type of isarithmic map that depicts the submerged bathymetry and physiographic features of ocean and sea bottoms. Their primary purpose is to provide detailed depth contours of ocean topography as well as provide the size, shape and distribution of underwater features.
Topographic maps display elevation above ground (topography) and are complementary to bathymetric charts. Bathymeric charts showcase depth using a series of lines and points at equal intervals, called depth contours or isobaths (a type of contour line). A closed shape with increasingly smaller shapes inside of it can indicate an ocean trench or a seamount, or underwater mountain, depending on whether the depths increase or decrease going inward.
Bathymetric surveys and charts are associated with the science of oceanography, particularly marine geology, and underwater engineering or other specialized purposes. Bathymetric data used to produce charts can also be converted to bathymetric profiles which are vertical sections through a feature.