In this report we use results from computational fluid dynamic (CFD) studies of the flow around different surface ships in order to investigate the wake, and in particular the underwater wake behind the ship. The study is motivated by the threat from wake seeking torpedoes and wake seeking sensors that are placed on submarines and autonomous underwater vehicles of different types. A practical example which indicates the usefulness of the study is a convoy situation with transport vessels and escort vessels. An incoming wake seeking torpedo would in the future be able to strike at either the transport vessels or the escort vessels, depending on the purpose of the attack. It is then important not only to identify a wake, but also to differentiate between different types of wakes. Sensor development has to date not reached as far as reliable wake seeking devices, but research in this area is carried out in several countries and demonstrators/prototypes are partially available. In the present study we focus on deriving characteristic wakes behind destroyer, transport vessel and submarine in order to compare these with each other. We also investigate the influence of speed and propulsion alternative. Large differences in the shape and turbulence intensity of the wake are observed for the destroyer and the transport vessel, but we also observe surprisingly large differences in shape and turbulences intensity depending on speed and propulsion alternative.