A phenomenon occurring in the wind-driven layer at the surface of the sea. In conditions of strong surface heating, a well-mixed warmer (and lighter) layer if formed, which is of limited depth because the stabilising density distribution inhibits vertical mixing with the deeper, colder water. At the bottom of this surface layer is a strong density gradient where the turbulence is suppressed and the Reynolds stresses are small. A given wind stress at the surface can thus accelerate the water to produce stronger surface currents in this case compared to an unstratified ocean. This is true because both the depth of the layer involved is smaller and the retarding stress below it is reduced. This creates the slippery sea phenomenon.