Wave-structure interaction (WSI) is a key problem in ocean and coastal engineering. This work presents a numerical wave tank for simulating WSI problems based on the improved Smooth Particle Hydrodynamics (SPH) open-source code DualSPHysics+ [1]. For fluid simulation, the combination of the δ-SPH density diffusion term and the Riemann dissipation term (δR-SPH) is used to ensure numerical stability while alleviating non-physical energy dissipation. The Velocity-divergence Error Mitigation (VEM) and Hyperbolic/Parabolic Divergence Clearing (HPDC) schemes are incorporated to suppress numerical density fluctuations and thus pressure oscillations. The Volume Conservation Shifting (VCS) scheme is used to improve the volume conservation during long-distance wave propagation. The Optimized Particle Shifting (OPS) scheme is introduced to improve the uniformity of particle distributions near the free surface. For structural simulation [2], a second-order discretization of the momentum equation is implemented, and a dynamic hourglass control scheme is introduced to improve the stress prediction and suppress the zero-energy modes. Several two-dimensional and three-dimensional benchmark cases are studied to validate the DualSPHysics+ numerical wave tank. The results show that compared with the original DualSPHysics model, the implemented δR-SPH method can effectively mitigate the non-physical energy dissipation and thus reduce the wave attenuation. The combination of VEM and HPDC reduces noise in the pressure field without introducing excessive dissipation. The VCS scheme enhances the conservation of local and global volumes in WSI simulations. The enhanced numerical wave tank is coupled with the Deep Reinforcement Learning (DRL) for the active control of floating structures in ocean environments [3]. The case of point-absorber array is studied to demonstrate the effectiveness of the two-way coupled active control framework.