Fluid-structure interaction occurs, for example, in wave impacts against reservoir walls, coastal structures - offshore platforms in the ocean, bridge piers, breakwaters -, in the sloshing phenomenon, tsunamis, coastal flooding, and biomedical applications. In the three-dimensional fluid-structure interaction simulation performed by the Lagrangian (meshfree) particle methods, the treatment of the collisions of the fluid particles against solid boundaries using a realistic reflective physical approach, replacing artificial computational techniques (such as virtual, ghost, mirror, dummy and dynamic particles, and unnatural repulsive forces) is an advance in the treatment of the contours, in the continuum domain. The benchmark study of a three-dimensional dam-break flow over a dry bed generating a wave that impacts a tall structure – a rigid obstacle fixed inside the reservoir – using the Smoothed Particle Hydrodynamics method coupled with the reflective boundary conditions is presented in this paper. The numerical results found are in good agreement with the previous literature data, proving the applicability of the reflective boundary technique – and encouraging its implementation – for the simulation of fluid-structure interaction problems in three-dimensional domains.