This study presents a numerical framework for analyzing the dynamic behavior of revetment blocks installed on a seawall under wave loading, using a fluid–rigid body coupled approach based on the Moving Particle Hydrodynamics (MPH) method \cite{1,2}. The target problem involves complex interactions among free-surface flows, rigid concrete blocks, and backfill stones, accompanied by large free-surface deformations and rigid-body motions, which are difficult to handle using conventional grid-based numerical methods. In the proposed framework, fluid motion is solved using the MPH method, which is derived from a physically consistent formulation based on analytical mechanics and enables stable simulation of free-surface flows. Interactions between rigid bodies, such as collisions and friction among revetment blocks and backfill stones, are modeled using a penalty-based contact model similar to the discrete element method (DEM). The motion of rigid bodies is computed using a passively moving solid (PMS) model, in which hydrodynamic forces obtained from the fluid solver and contact forces arising from rigid–rigid interactions are consistently coupled to determine translational and rotational motions. The coupled simulation algorithm advances in time by sequentially computing hydrodynamic pressures and forces, rigid-body contact forces, rigid-body motions, and particle positions. Two-dimensional numerical simulations are conducted to model wave-induced loading on a low-height seawall under construction. Multiple computational cases corresponding to different tide levels and wave conditions are examined to reproduce experimental settings reported in a previous study \cite{3}. Through these simulations, the applicability and numerical stability of the proposed MPH-based fluid–rigid body coupling framework for revetment block analysis are demonstrated by qualitatively reproducing characteristic block motions and damage processes. The developed methodology provides a basis for future studies toward quantitative investigations of wave-induced forces and stability mechanisms of coastal protection structures.