This paper proposes an improved soil-water-structure coupled interaction model within the framework of smoothed particle hydrodynamics (SPH). The continuous penetration process of the spudcan in clayey soil was investigated along with the concomitant variation of pore water pressure. The proposed method enables the efficient capturing of excess pore water pressure variation in soil undergoing large deformations. Verification and validation performed using previous numerical investigations and centrifuge test data indicate that the proposed model is valid, robust, and effective. This model can be employed to solve various penetration problems and other problems involving complex soil-water-structure interaction and large soil deformations.