De Slufter is a dramatic saltwater inlet just north of De Koog — the one place on the entire Dutch coast where the North Sea runs directly into the dunes without any dike standing in the way. The result is a wide valley of salt marsh, tidal channels, and dune slack that feels genuinely wild. At high tide the sea pushes several hundred metres inland; at low tide egrets and dunlin pick through the exposed mud.
The reserve is easily reached on foot or by bike from De Koog — a 20-minute ride north along the beach road brings you to the access point. Walking trails loop around the valley; the full circuit takes about two hours. Note that the western side is closed from March to September to protect nesting birds, but the southern section remains open year-round. The birdwatching is excellent at any time of year: spoonbills, marsh harriers, avocets, and dozens of wader species use De Slufter as a staging post.