The marine controlled-source electromagnetic (CSEM) method is an important tool for offshore exploration. It allows recovery of subsurface resistivity, a key hydrocarbon (HC) indicator, using modeling- and inversion-based interpretation of the EM data acquired on the seafloor. Application of CSEM can reduce risk and optimize drilling operations, as well as improve estimates of HC reserves. The CSEM workflow consists of the following main steps: feasibility study, survey design, data acquisition, processing, and interpretation. Feasibility study and data interpretation rely heavily on 3D EM modeling to properly select and plan surveys and recover the 3D subsurface resistivity image. Detection of deep small targets immersed in anisotropic environments is a challenging task for the current CSEM technology, making it essential to employ the best practices in performing reliable feasibility studies. To manage this task, a skilled modeler needs to take into account all available geological and geophysical data to build a 3D Earth model and utilize accurate 3D EM modeling software. The fast and reliable 3D EM modeling that can accurately handle arbitrary anisotropic resistive media with complex structural interfaces and HC reservoirs would make a crucial contribution to the success of CSEM technology.