This chapter presents the flexural and repeated impact performance of stainless steel-lightweight high ductility cement composite (LHDCC) beams for marine structures. Repeated drop-hammer tests and LS-DYNA simulations are used to investigate the effects of connector spacing/type, core thickness, material type, and layering on response and damage. Three failure modes are identified: flexural with bond-slip (partial composite), pure flexural (full composite), and shear (low core shear strength). Double-layer cores limit crack growth and improve residual performance, and rubberized LHDCC (RLHDC) reduces residual deformation by 60% relative to LHDCC through added energy absorption. The continuous surface cap model (CSCM), calibrated by uniaxial and triaxial tests, estimates impact histories, failure models, and energy dissipation. Repeated impacts cause lower average impact force, higher peak displacement, and reduced global stiffness. The core thickness strongly affects force and stiffness, while number of layers governs displacement. In flexural failures, the steel plates dominate through plastic deformation, whereas in other modes the concrete core contributes more via crack propagation. Increasing stud spacing reduces energy absorption, the steel contribution drops by about 30–35% as spacing increases from 100 mm to 150 mm. A trilinear load-displacement relation incorporating strain-rate effects and composite action support an accurate modified single-degree-of-freedom (SDOF) model.