The observation of an isolated lens with a layer of constant temperature, salinity, and density within the upper thermocline of the southwestern Sargasoo Sea is reported. Temperature and salintiy as well as a high oxygen content indicate the Gulf of Cadiz as the area of formation. The age of the lens appears to be 3--4 years. Atmospheric conditions are favorable for deep convection in the Gulf of Cadix during winter months, but no dramatic event could be detected. The hydrographic and dynamic background of the lens in the Antilles Current area is discussed with reference to Iselin's (1936) standard data.