Results of an experimental study of the convective heat and mass transfer processes for downward freezing from a horizontal surface into seawater at 35 parts per thousand, i.e. at oceanic salinity, are presented here. Liquid supercooling of about 5.0-degrees-C was detected at the cooling surface before freezing began. Supercooled water was also detected far from the cooling surface, under some conditions. This supercooling, before freezing, allowed the possibility for density extremum effects to arise under some conditions of low ambient water temperature and large extracted heat flux. After freezing, however, flow visualization revealed that the flow was downward, below the freezing surface. At the high cooling and freezing rate used in these experiments the ice layer and water-ice interface salinities were found to be only weakly dependent on the ice growth rate. Convective heat transfer rates were found to be strongly affected by solute rejection upon freezing.