Bathymetric Maps

http://www.gulfofmaine-census.org/about-the-gulf/physical-characteristics/bathymetry/

Bathymetric maps look at sea floor elevation. It is essentially the underwater counterpart of an above water topographic map.  It serves to measure the depths of water.  The map above is showing the gulf of Maine and looking at the depths of water throughout the area as measured through meters. It also uses false colors in order to display deeper bodies of water in comparison to more shallow areas.