This paper presents past and recent water management in the area called the Vistula Delta Fens (Zulawy Fens). This area (56 x 56 km) is located at the outlet of the Vistula River to the Baltic Sea, at the shore of the Gulf of Gdansk. A large part of the area (30%) is located below sea level as potentially submerged depressions. A multitude of rivers, channels, ditches and pumping stations have been constructed here during several centuries. The area is characterized by highly productive alluvial soils, surface water with a high potential for fish-farming and fishery, and attractive tourist areas at the banks of the rivers and channels. Historically, floods have occurred repeatedly as a result of: (i) – breaks in the dams along of big rivers, e.g. after heavy rains and high water levels (in summer); (ii) – dam breaks caused by accumulation of ice-cakes in winter or during spring times; (iii) – dam breaks after storms on the sea with increasing sea water levels at the river outlets (mainly in winter); (iv) – overflow of water into flat land after heavy rains followed by slow drainage of water from the fields, ditches, channels and pumping stations (in summer); (v) – overflow of water into depressions and swamps below sea level after interruptions of, or decreases in, the pump operations at the pumping stations.