Sea
The North Sea is a peripheral sea of the Atlantic Ocean. Spread over the four winds it has the following boundaries: to the west England and Scotland; to the south France, Belgium, the Netherlands and Germany; to the east Denmark, Sweden and Norway; to the North the Shetlands. The surface of the sea amounts to 545 000 square km; this is ± 19 times as large as Belgium. The North Sea has an average depth of 100 meter with extremes of 274 meter and 13 meter.
The temperature of the surface water varies between 3 and 6 degrees C at the end of the winter and increases to 14 a 17 degrees C during the summer months. The salt content amounts to 32 to 35 per mille. The bottom relief is flat to slightly undulating. Sandbanks build the elevations, whereas the sea currents scour deep channels. In Nieuwpoort the average tide difference is 4,04 m. One tidal movement takes exactly 12 hours and 54 minutes.