This study investigates beach morpholithodynamics within the context of superimposed wave and tidal influences. Findings from beach profile surveys are analyzed, with a specific focus on beaches exhibiting an uneven alongshore distribution of sediment due to the development of megafestoons (large-scale sand waves) and their associated systems. The paper presents findings from morphometric monitoring (2005–2022) of a stable megafestoon system that has persisted for at least 65 years. Key morphometric and morphodynamic parameters for this system are established, including deformation volumes and changes in its spatial configuration over specific time intervals. While the precise causes and mechanisms for this alongshore heterogeneity remain unclear, several observations provide insight: the spatial instability of system components, sediment deformations extending to the depth of closure, and the alongshore migration of accumulative features in the direction of longshore sediment transport. These factors suggest that the system represents a self-organized response to spatiotemporal variations in wave approach angle. In contrast, it is likely that stable megafestoon systems on open ocean coasts form through different mechanisms.