A dual-beam interferometric synthetic aperture radar measures remotely two radial components of the ocean surface current from a single flight pass. Combining two passes over the same area, all three orthogonal components of the surface velocity can be retrieved. An experiment is conducted near the Gulf Stream (GS) boundary. A sharp change of the surface velocity of about 1 m/s over a 500 m lateral distance is measured. The wind and wave condition is dominated by a 14-s swell system and low wind velocity. The wave variance inside GS is about twice the wave variance outside the GS in the present data set. The difference in the wave variance is considerably higher than that can be expected from wave-current interaction. An ocean current system with strong shears such as the GS is a wave guide and can trap waves with the right combinations of wavelengths and propagation directions. Numerical calculations suggest that the wave properties of the data set may satisfy the conditions of wave trapping by the GS. The standing wave pattern on the GS side of the sharp velocity front, indicative of the long swell bouncing off the current front, also offers support for the wave guide hypothesis. In this respect, the Gulf Stream can be considered the nature's hydraulic breakwater that can attenuate about 50% of the incident wave energy generated by storms. Its role in protecting the U.S. coastlines in the Atlantic Ocean cannot be overstated.