Rising tidal waters breach a channel-bounding spit at mid-tide to carry cool, saline waters into the ebb-dominant channel of the Ria do Barqueiro. Foam lines form an evolving pointed and curving pattern bounding more and less saline waters, and mark the surface limits of the intrusive front. Repeated measurement by radiometer demonstrate the initial presence of three thermally identifiable water masses, at I6.5°C, 17.5°C and 19.8°C, and the homogenization of temperature in less than half an hour.