In this paper, a fully coupled fluid structure interaction (FSI) method is used to investigate the hydro-elastic response of a fully submerged standing structure under seismic excitations. Two different domains (solid and fluid) are modelled by mesh based and meshless methods, respectively. Solid domain is modeled by finite element method (FEM) and fluid domain is modeled by smoothed particle hydrodynamics (SPH). Coupling between FEM and SPH is implemented via contact mechanics, and this method differs from others in the way of coupling mechanism. Invading SPH particles are solved together with finite elements by using contact mechanics, then, a fully coupled method is achieved. In the scope of this research, different seismic excitations are applied to a rectangular tank. Half of the tank is filled with water and a submerged rubber plate is attached to its mid bottom. Thus, two-dimensional motion of rubber plate and water is investigated experimentally and simulated numerically.