The demand for the reduction of maintenance of structures especially those in marine environments is increasing and more is asked of structures in terms of durability and capacity. Fibre reinforced polymer (FRP) could be a solution to reduce the maintenance of these structures, because of its high durability and as an ad-vantages lighter structures could be constructed. The use of FRP in lift gates can be really attractive to optimize lift gates drive mechanisms by limiting the gates dead weight. Though because it’s a relatively new material in civil engineering structures, its behaviour under dynamic loading is not yet fully known. However, it is known to be a critical aspect of the design. To investigated the dynamic behaviour of a lift gate made in FRP a case study was conducted regarding a renovation project for a guard lock located in the Juliana channel in Maastricht, the Netherlands. This guard lock serves not only as a guard lock to regulate the water level in the channel preventing floodings but it also serves as a navigation lock, that provides passage for ships using the Juliana channel. To come to a design first seven different design alternatives for the gate were drafted. From these alternatives, the Lens gate and the Arched gate were chosen for further analysis. The dynamic analysis was carried out using both a mass-spring model and a beam model. The resulting eigen frequencies were then compared to the ones obtained from a 3D-numerical model made with ANSYS. To be able to answer the question of which gate design is less susceptible to hydrodynamic loading the excitation frequencies, due to the flow underneath the gate and the waves, that could cause the gate to vibrate where determined. This was done for both vertical and horizontal vibrations. From this investigation it was concluded that both gate designs can be excited by (stationary) waves and that the Arched gate is susceptible to vertical vibrations due to flow. Therefore the choice which gate design would be best has been for the Lens gate. However some changes to the gate dimensions could improve the dynamic behaviour of the Arched gate. And because other aspects of the design should be taken into account, e.g. the integration of the gate within the lock system, no definitive conclusion can be drawn.