Watersportvereniging Neptunus is a members' sailing and motor-boating club with a marina situated in the Koornwaard nature reserve, on the Maas at kilometre marker 215, just outside 's-Hertogenbosch.

The harbour lies in a quiet sandy lake directly connected to the river, and the surrounding floodplain is home to Konik horses, kingfishers, spoonbills, and beavers.

The club offers around 150 permanent berths and welcomes visiting boaters subject to availability. The site is open year-round and includes a club vessel where light refreshments are served.

Because the marina sits within a flood plain, the natural environment is notably rich, and despite its proximity to the city, the atmosphere remains peaceful. Visitors arriving by water have direct access to the wider floodplain area of the Koornwaard reserve.