1. A device comprising: a memory element configured to store contour line data for one or more bodies of water, the contour line data indicating all of the geolocations of underwater terrain that exist at a depth of water; and a processing element in communication with the memory element and the display, the processing element configured to identify a high contour line density area of the contour line data having at least three adjacent contour lines within a threshold distance, update the contour line data to reduce contour line density in the high contour line density area by selectively removing at least a portion of the at least three adjacent contour lines in the high contour line density area, and store the updated contour line data in the memory element.