Why are concrete caisson quay walls especially suitable in regions with small tidal ranges?

Concrete caisson quay walls are especially suitable in regions with small tidal ranges, such as the Mediterranean, because the slightness of the tidal variation keeps the required depth of the wall to a minimum.1

In civil engineering, the net clear height of a quay wall must span the distance from the lowest seabed level required for navigation to an adequate freeboard above the highest high tide. By minimizing the difference between low and high water levels, regions with small tidal ranges allow for shorter, more economical quay wall structures. When the depth from ground level to the final dredged bottom is not excessive, precast concrete caissons can be efficiently floated into position and sunk onto a prepared bed to serve as a stable, permanent quay wall.21