"This educational film explains the seepage processes through a dike. For this purpose, the prevalent methods for the determination of the phreatic line are presented. A model dike was developed for the shooting and built in an experimental rig. The phreatic line is determined by analytical, numerical and experimental methods. These methods are then compared with each other. In the second half of the film, all methods are used to determine the phreatic line of the dike with a watertight core. Again all methods are then compared." This is part of the Open Educational Resources Initiative by the Faculty of Civil Engineering of the RWTH Aachen University.