The Nieuwe Waterweg is a major tidal estuary and navigation channel in South Holland, Netherlands, serving as the primary maritime artery connecting the Port of Rotterdam directly to the North Sea. This man-made waterway, opened in 1872, is a deep, saltwater corridor characterized by significant commercial shipping traffic. Unlike other Dutch delta outlets that have been closed off, the Nieuwe Waterweg remains the only fully open, lock-free connection between the Rhine-Meuse river system and the sea. The waterway has been repeatedly deepened over the twentieth century, with its navigation channel now reaching depths of 16.2 meters. As a tidal estuary, it experiences the full influence of North Sea tides, creating dynamic currents that mix saltwater with the freshwater inputs from the Nieuwe Maas and Oude Maas rivers. The banks are heavily developed for port infrastructure, with urban centers like Vlaardingen and Schiedam located along its northern shore.