<p>To address the challenges posed by large tidal ranges and shallow-water conditions on the performance of nearshore breakwaters, this study proposes a closely spaced inclined-pile breakwater (CSIPB), based on the engineering needs of a new energy project in the Nangang area of Tianjin Port. Hydrodynamic experiments were conducted using a 1:25 scale three-dimensional physical model in an L-shaped wave basin, at various water depths, wave heights, and wave period conditions. The wave transmission, reflection, and energy dissipation characteristics of the structure were systematically evaluated, and its harmonic response characteristics were analyzed using fast Fourier transform. The results indicate that the CSIPB exhibits strong adaptability to tidal variations. Wave energy dissipation dominates at high water levels, whereas wave reflection becomes the primary response under low water levels. Harmonic analysis further reveals that high-frequency harmonic components are mainly reflected back toward the incident side and become increasingly pronounced with increasing wave height and wave period. At shallow-water irregular wave conditions, although the effectiveness of the breakwater in controlling high-frequency wave components is reduced, the structure remains capable of effectively attenuating fundamental-frequency wave energy. Based on these findings, the proposed CSIPB is suitable for typical shallow marine environments with large tidal ranges and demonstrates good adaptability across a range of operational conditions.</p>