This paper presents the adaptation of the Transmission-Line Matrix (TLM) electromagnetic simulation method to the case of the propagation of a radar electromagnetic signal over a sea water patch. The TLM is a full-wave and numerical method; in order to gain computation time, it is combined with ray-tracing in our approach. We propose an overview of the advantages and disadvantages of the use of the TLM method for the electromagnetic simulation of a radar observation. Then, we give details about the implementation of the TLM to model the interaction between an impinging electromagnetic wave and the ocean surface; this includes some particular modifications of the classical TLM technique, and a combination with spectral sea surface rendition methods. Using our simulation method and the radar equation, normalised cross sections can be derived and compared with models. Alternatively, some imagery process can be carried out on small areas using the synthetic aperture technique. Since virtually any sea/radar configuration can be explored, including the presence of manufactured objects in the midst of the simulated sea patch, the flexibility of our simulation tool is demonstrated.