1. A volume of hydrocarbon obtained from an area that contains a subterranean hydrocarbon reservoir, the hydrocarbon obtained by: performing an underwater controlled source electromagnetic (CSEM) survey of the area to provide electromagnetic field data at a plurality of discrete frequencies between 0.01 Hz and 60 Hz for specific source and receiver locations; performing a migration of the data for the source and receiver locations; and applying an imaging condition to the migrated data at each subsurface location to produce an image parameter which represents a desired physical property of the subsurface; identifying the hydrocarbon reservoir from the values of the image parameter subsurface locations; penetrating the identified hydrocarbon reservoir with a hydrocarbon-producing well; and extracting the hydrocarbon from the reservoir using the well.