<p>Porous structures are widely used in subsea equipment, whereas their slamming characteristics during water entry are still not well understood. Physical experiments and three-dimensional smoothed particle hydrodynamics (3D SPH) models were conducted to examine the effects of porosity and entry velocity on the water-entry slamming of porous plates. The numerical and experimental results are in good agreement. Three porosities and entry velocities are considered at experiment, and the slamming pressures and flow field are recorded. The numerical error of the peak slamming pressures is less than 5% relative to the experimental average value. The results indicate that porosity and entry velocity significantly affect the water-entry slamming of porous plates. Specifically, the dimensionless peak load coefficients exhibit a quadratic decreasing trend with increasing porosity, whereas the peak loads increase quadratically with entry velocity. Furthermore, the surface pressure distribution is strongly influenced by porosity and pore arrangement. As porosity and the number of pores increase, the spatial continuity of the pressure distribution diminishes, while discontinuity becomes more pronounced. When the pore arrangement pattern and the number of pores are kept constant, the pressure distribution exhibits a distinct central cross-shaped pattern at porosities of 15%, 20%, and 25%, whereas a multi-peak pattern emerges at higher porosities of 30%, 40%, and 50%. When the porosity is fixed at 20%, significant differences in surface pressure are observed among plates with different pore arrangements. The porous plate with a larger number of pores combined with smaller pore diameters and spacings experiences lower slamming loads. These findings elucidate the mechanisms of pore-induced slamming dynamics during the water entry of porous structures, providing critical theoretical support and design guidance for the deployment and recovery of subsea equipment.</p>