Hydrocarbon detection in Sea Bed Logging (SBL) is a very challenging task for deep target reservoir. Response of electromagnetic (EM) field from marine environment is very low and it is very difficult to predict deep target reservoir below 2500m from the sea floor. Straight and new EM antennas at 0.125Hz frequency are used for the detection of deep target hydrocarbon reservoir. The proposed area of the seabed model (16km16km) was simulated by using CST (computer simulation technology) EM studio based on Finite Integration Method (FIM). Comparison of straight and new antenna for different target depths was done in our proposed model. Total electric and magnetic fields were applied instead of scattered electric and magnetic fields, due to its accurate and precise measurements of resistivity contrast. From the results, it was observed that straight antenna at 0.125Hz shows 40.30 resistivity contrast at target depth of 1000m where as new antenna showed 304 resistivity contrast at the same target depth for E field. It was found that E field response decreased as the target depth increased gradually by 500m from 1000m to 2500m at different target depths with constant current (1250A). It was also investigated that at frequency of 0.125Hz, new antenna gave 54 better delineation of hydrocarbon at 3000m target depth. This is due to focusing of electromagnetic waves by using new antenna. This EM antenna may open new frontiers for oil and gas industry for the detection of deep target hydrocarbon reservoir below the seafloor. © 2011 IEEE.