Bathymetry's the study of underwater depth of the third dimension of lake or ocean floors. In other words, bathymetry's the underwater equivalent to hypsometry. The name comes from Greek βαθυς, deep, and μετρον, measure. Bathymetric (or more correctly Hydrographic) charts are typically produced to support safety of surface or sub-surface navigation, and usually show seafloor relief or terrain as contour lines (called depth contours or isoba… (More on Bathymetry)