Due to their numerous advantages, Geotextile Sand Containers (GSCs /or Geobags) are getting increasingly popular as an alternative to conventional hard (rock / concrete) structures. This study attempts to evaluate the significance of the most important engineering properties and their influence on the hydraulic stability of GSC-structures. The most important engineering properties of GSCs are the mechanical properties of the geotextile material, the sand fill ratio, type of the fill material, the interface friction, etc. In fact most of these properties will affect the deformation of GSCs and the movement of sand inside the container. More importantly, these properties are interrelated. The importance of these aspects has been highlighted in many studies and projects worldwide. However, the knowledge about the influence of the sand fill ratio, the properties of fill material and the interface friction of GSCs on the hydraulic stability of GSC-structure is still very poor. Therefore, a series of experimental investigations were conducted, in order to better understand their effect on the hydraulic stability and to develop a computational tool and simple formulae for the hydraulic stability of different types of GSC-structures subject to different wave conditions. This paper contains some selected findings from these experimental investigations, which were performed at Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI). Furthermore, the sensitivity of each GSC property on the hydraulic stability and new hydraulic stability nomograms are presented, including the implications for the engineering practice.