Among the ceramic sherds dredged from the seabed of the ‘Akko Marina were some bowls with a glaze of unusual silvery-black appearance. This study was conducted to define the main factor leading to the changes in color under sea water. The sample included glazed vessels found on land and glazed vessels from the sea. Significant differences in sulfur content were observed between the two sets of glaze: the on-land vessels contained no sulfur, whereas the vessels from the sea contained sulfur, obviously originating in the sea water, thus creating sulfides of lead in the glaze.