Visit Het Sas van Bornem on the Old Scheldt in combination with the Marnix van Sainte-Aldegonde Castle. In fact, the area around the Old Scheldt is completely set up for your recreation, including a restaurant in the former sash house. The Sas van Bornem is a drainage sluice in a tributary of the Scheldt, the Old Scheldt. In the 13th century this part was closed off and it was navigated until 1950.
More information can be found here.