When a navigation lock, dam, or any other structure with water is subjected to an earthquake, one of the dynamic loads will be hydrodynamic pressure. This is the pressure exerted by the fluid on the structure as a result of the different behavior in motion of solid and fluid. To determine this pressure there are several available methods which focus mainly on large dams or fluid storage containers. However, the hydrodynamic behavior of these types of structures is different and these methods may or may not be applicable for navigation locks. Therefore an analysis is made to determine the factors that contribute to the hydrodynamic pressure distribution on large lock structures. As a case study the Third Set of Locks Project of the Panama Canal is used. This expansion project ensures that the Panama Canal can process larger ships than the current Panamax class of ships, which dimensions are limited by the existing locks. Therefore larger locks are required which will operate next to the existing locks. The new locks are planned to be operational in 2014-2015. The Panama region is prone to earthquakes which could result in large hydrodynamic pressures on the locks. For the evaluation of hydrodynamic pressure on large lock structures, two analytical (1D and 2D) and one 2D finite-element model using DIANA are made. Three main aspects that contribute to hydrodynamic pressure are treated in detail: - Lock dimensions and water levels; - The effect of surface waves on the hydrodynamic pressure distribution; - The flexibility of the structure.