Frisian Islands Chain and Dikes in the Netherlands
The West Frisian Islands, in a chain off the coast of the Netherlands, separate the North Sea from the Wadden Sea, an intertidal zone between the continental coast and the islands.
While the North Sea is deeper and appears dark navy blue here, the Wadden Sea has a greenish brown color, as it is a shallow body of water with tidal flats and wetlands rich in biological diversity.
The biggest and most populated of the Frisian Islands is called Texel. It is also the westernmost of this archipelago, and forms the largest natural barrier between the two seas. The dune landscape on Texel is a unique habitat for wildlife.
Below Texel and the Wadden Sea is a body of water formerly known as the Zuiderzee. After being closed off from the North Sea by a dike, it was separated into two lakes: the IJsselmeer and the Markermeer, which are in turn separated by another dike called the Houtribdijk.
These dikes are visible in the full image as lines where the color of the water changes abruptly from dark brown (Wadden Sea), to dark green (IJsselmeer) to bright green (Markermeer).