Active contour methods like snakes, have become a basic tool in computer vision and image analysis over the last years. They have proven to be adequate for the task of finding boundary features like broken edges in an image. However, when applying the basic snake technique to synthetic aperture radar (SAR) remote sensing images, the detection of varying-contrast edges may not be satisfying. This is caused by the special imaging technique of SAR and the commonly known specklenoise. In this paper we propose the use of asymmetric external energy terms to cope with this problem. We show first results of the method for the detection of edges of tidal creeks using an ENVISAT ASAR image. These creeks can be found in the World Heritage Site "Wadden Sea" located at the German Bight (North Sea).