Abstract: The southwestern coastal region of Hainan Island features diverse sand wave morphologies shaped by complex formation mechanisms. These migrating sand waves pose significant threats to marine infrastructure, including the exposure of submarine pipelines and scouring of pile foundations. This study employed hydrodynamic observations, geological data, and multibeam bathymetric surveys to systematically analyze the formation, evolution, and controlling factors of nearshore sand waves. By examining hydrodynamic and sediment transport processes, it reveals the development patterns and migration mechanisms of sand waves in the study area. The study further quantifies the relative influence of tidal currents and waves on sand wave formation, as well as sediment initiation and transport capacities. Results indicate that sand waves shaped by modern hydrodynamics exhibit strong mobility, with crescentic sand waves showing average migration rates up to 18.73 m/a, while paleo-sand ridges remain largely immobile due to high shear resistance of sediments. Migration directions align with dominant near-bottom flows: northward or along sand ridge–trough paths in flood-dominated zones, and southwestward in ebb-dominated zones. In equilibrium zones, symmetric sand waves predominate with reduced mobility. Sand waves are primarily concentrated at 22-42 m water depth, with crescentic forms in deeper zones (＞10 m/a) and symmetric forms in shallower areas (＜5 m/a). Coarser sediments (＞0.2 mm) favor the development of fast-migrating crescentic sand waves, while finer sediments typically form slower-moving symmetric waves.