Not only the town centre but also the surrounding area is ideal for exploring. In the polder (reclaimed land) at Zwartewaal, there's a small nature reserve called the Holle Mare that's well-known with bird watchers. The creek and grasslands are home to geese and gadwall and in the winter, you'll see the Eurasian widgeon. In the reed beds, you can spot the reed bunting, the shy bittern and the brown harrier so take your binoculars with you!
You can take a refreshing walk along both shores of the Brielse Meer in every season. There are various bars and restaurants for a culinary or sanitary break.
The themed hiking routes across Voorne-Putten are also recommended, such as the Boten en Bakens (Boats and Beacons) route that starts in Brielle. And there are more themes, all of different walking distances. View them all at https://www.opvoorneputten.nl/wandelroutes.