The marine EM exploration method has become a legendary and complimentary technique to other geophysical methods in the offshore hydrocarbon exploration. There are two EM exploration methods: marine magnetotelluric (MMT) and controlled-source electromagnetic (CSEM). MMT is a natural source method, which utilized earth''s natural electromagnetic field as a source field. The commercial survey applicability of CSEM for offshore hydrocarbon exploration use a mobile horizontal electric dipole (HED) and an array of seafloor receivers,which measured the EM fields. Integration of MMT and CSEM data significantly enhances the exploration efficiency and minimizes the risk of dry well before the offshore drilling.