The substructures of sea-crossing pile foundation bridges, which are located in zones with active seismicity, are vulnerable to earthquakes and water forces that induce damage during their beneficial operation. This study investigated the behavior of this type of bridge under the combined influence of water forces represented by currents and waves during seismic actions. This study proposed a method for analyzing Morison equation and simplified its inertial and drag coefficients. A new technique called the reality water-structure-earthquake interaction test (RWSEIT) has been developed to study the hydrodynamic pressure distribution and acceleration along the height of the pile foundation of a 1:20 scale concrete model.