In 1989 an experiment in Loch Linnhe, Scotland, was conducted to improve the understanding of radar images of internal-wave wakes generated by ships. During the experiment a multi-frequency synthetic-aperture radar (SAR) image containing several bright narrow V-shaped wakes was obtained during a period of low wind speed. One of the wakes imaged is caused by internal waves generated by a ship that was participating in the experiment. Three other wakes were also imaged which were generated by fishing vessels. The wakes of the fishing vessels are different in appearance to the internal-wave wake generated by the experiment ship. Given that the displacement of the fishing vessels is about four orders of magnitude less than the experiment ship it is unlikely that they could produce internal waves that could be detected by the radar. The fishing vessel wakes observed at two different radar frequencies can, however, be explained by the mechanism proposed by Munk et al. in 1987.