2 ponds (or lagoon) were studied in order to establish the economic possibilities of their exploitation for oysters. Bathymetric and sediment maps were produced using methods described. They indicate a morphological similarity between the ponds, with a superficial broken bed and a regular, flat or gently sloping bed beyond 7 m, the general form reflecting the aerial relief of the adjacent `coast'. The deeper regions had mud or clay sediment, while the edges of the ponds were covered with sand. In more detailed studies it was evident that the banks of Diane were more regular and steep than those of Urbino, and that only in the latter was there a good relationship between the depth of water and the carbon/nitrogen ratio. Differences are thought to relate to the histories of the 2 ponds, Urbino having experienced less communication with the sea.