In the R&D project Underwater Signatures it is of interest to simulate wakes far downstream ships and submarines. A literature review has been conducted to identify suitable simulation methods, and here three are presented: 3D, 3D+t, and 2D+t. In the 3D method a simulation is first performed for the object that generates the wake, the so called wake-generator, and data from a near-wake cross-section is used as inletcondition to a wake-simulation. In the more efficient 3D+t method the wake is simulated in a short domain with periodic boundary conditions. The initial state comes from a simulation of the wake-generator or from a synthetic representation of the wake. In the even more efficient method 2D+t a cross-section of the wake is simulated. The most interesting method is found to be 3D+t, since it is expected to capture wake fluctuations detectable by sensors with reasonable computational resources. First, it is of interest to evaluate the method initiated from a simulation of the wake-generator, and later with an average flow field and synthetic fluctuations from a RANS of the wake-generator. The 2D+t method is of interest to study how large-scale structures downstream ships affect the redistribution of surface surfactants, which under certain conditions can be detected with Synthetic Aperture Radar tens of kilometres downstream the ship.