The theme of the entire composition is the sea. It is inserted in a large rectangular swimming pool with rounded corners, surrounded by a walkway that runs from one side to the other, enclosed in turn by a short staircase just below the street level of the square. The water gushes from the rocks in different points: under the Oceano cart it fills three pools, before pouring into the largest pool. The three basins were not part of Salvi's original project, but were added following the changes made by Giuseppe Pannini, who replaced it after his death. Another substantial modification concerned the subjects of the two lateral statues, which initially represented Agrippa and the "virgin Trivia". Given the breadth and complexity of the work, many sculptors were involved in the realization of the various statuary groups.