After two decades of development, the Surface Water and Ocean Topography (SWOT) mission launched on December 16, 2022, pioneering the use of Ka-band Radar Interferometry (KaRIn) for measuring water surface elevation and achieving wide-swath, two-dimensional altimetry. Rigorous validation against in-situ observations in this study demonstrates that KaRIn achieves enough accuracy to resolve sub-100 km oceanic processes, with measurement errors four times smaller than anticipated. These results confirm SWOT’s transformative capabilities for advancing oceanographic research, validating the high fidelity of the advanced mooring systems and establishing a robust foundation for future applications of the wide-swath altimetry.