This paper present two-dimensional forward modeling of marine controlled-source electromagnetic data for the purpose of hydrocarbon mapping. The forward algorithm employs a staggered-grid finite difference solution to the total-electric field Helmholtz equation. Solution are achieved through a) an optimal grid technique that extends the boundaries of the mesh outward from the region of interest using a minimal number of nodes, and b) a direct matrix solution technique that allows for the simultaneous solution for all sources. The forward modeling provides qualitative understanding of electromagnetic signals behavior as it propagates through hydrocarbon and conductive saline fluids bearing layers at depth. © 2011 IEEE.