The marker Sea (Dutch sea - the sea ) is a 700 km ², up to 4 m deep lake in the Netherlands. It was created in 1976 by ​​the construction of Markerwaarddijk of Enkhuizen to Lelystad. This separates the Marker lake in the north- east by the IJsselmeer and it runs the main road N302. In the southeast the waters adjacent to (southern and eastern ) Flevoland, an artificial polder. Originally, the Marker lake in the Zuiderzee as Flevoland, or Noordoostpolder should be drained as Markerwaardpolder, however, the region has now established itself as a recreational area, so that the implementation of this plan is unlikely. More arising from the former Zuiderzee inland lakes are IJsselmeer and the IJ, the bay in Amsterdam, which is also called Buiten - IJ and which is separated by the Oranje locks from the single - IJ.

A popular destination is the eponymous island of Marken, connected by a road to the mainland. To the west is a bay called Gouwzee that is largely separated from the open sea by the island marker brands and their dikes.

The area is also known for its cheese production. Not far from the Gouwzee is Edam, eponymous for the Edam cheese with red rind.

Other notable towns are at the Marker lake Volendam ( Edam- Volendam to ), Hoorn, Enkhuizen, Lelystad and Almere. South Flevoland then lies on the nature reserve Oostvaardersplassen.