Mesoscale eddies are large whirlpools in the ocean with diameters of hundreds of kilometers. Their influence can extend to depths of 1000 m or greater. Oceanographers are only now beginning to document the prevalence, extent, and influence of such features in the world ocean. The availability of third-generation ocean color imagery from the Moderate Resolution Imaging Spectroradiometer-MODIS sensors aboard NASA's AQUA and TERRA platforms, and support for direct observation at sea, have now allowed characterization of such an eddy interacting with the Orinoco River plume (ORP) while traversing the eastern Caribbean basin. The ORP extends seasonally across the basin from August through November, 3 to 4 months after the peak of the seasonal rains across northeastern South America. At this time, a thin plume of relatively low-salinity water, rich in phytoplankton and bearing significant amounts of colored dissolved organic matter (CDOM), covers a large swath of the basin, offering a striking contrast to the intensely blue oceanic waters of the adjacent northwest Atlantic Ocean.