Have you ever wondered how polders are born? For those of you who might not know, a polder is drying the hell out of a water area (such as a lake or portion of the sea). The Netherlands boost some 3000 polders.
In the picture above you can see the basic of polder creation: a ship fully loaded with dirt positions itself and starts dumping it into the water. Easy-peasy. The process is repeated until you create an artificial lake, to be later drained.