Within the framework of the workpackage 4c: “Flexible coastal defence with geosystems”, which is part of the workpackage 4: “Morfodynamics of the North Sea and coast” several problems are formulated with respect to the application and design of Geosystems. This is performed within the Delft Cluster project “Sustainable development of North sea and coastal zone”. The formulated problems are: 1. Stability of geocontainers under wave attack and/ or currents. 2. Positioning accuracy of geocontainers. 3. Required strength of the geotextile during the placement of geocontainers. 4. Sustainability of geocontainers with respect to UV load, ageing process and mechanical loads. The first subject is suitable for research in Delft Cluster 2. Taking in mind that wave loads are a larger problem with respect to the stability than currents, the former is selected for research. The second and third topic have been investigated in Delft Cluster 1. This resulted in an improvement of knowledge. The main goal in the long run, providing a thorough insight in the risks of applying geocontainers, can be realised by backing up the research with practical experience and scale model tests. The costs of these are however too much to include in Delft Cluster 2. UV loads and ageing processes of geotextile are subjects in the domain of the manufacturers of geotextiles. Therefore, it is decided, in close cooperation with the Centre for Civile Engineering Research and Codes (CUR), to focus on the stability of geocontainers under wave attack. This report describes and analyses the large scale model tests which have been executed to determine the stability of geocontainers.