This dam was projected in a gully suited for seaworthy ships. This gully had to stay intact for its economical value for Rotterdam and Antwerpen. First they had to built locks so that shipping was ensured during the building of this part of the dam. First they created a construction site near Willemstad. This was a dock of 350 meters wide and a length of 850 meters. After constructing the locks and placing the lock-gates the rest of the dam could be build. This was done by 14 caissons. These waterproof caissons were prefabricated on a nearby construction site and tugged to their final position.