Sportfishermen do not come in Rockanje empty-handed at home! It could be fished from a boat at sea or from the beach. Every angler finds a suitable place. And the fish bites well. Eel, perch or trout, but also whiting, dab or sole are richely present in the water.
Sport fishing is connected to certain regulations. To float into the water you need next to the rural sport angling permit, depending on the kind of fishing water and the administrator, a permit: http://www.sportvisserijnederland.nl/vispas/english/.
Sea fishery is free. In the fishing zone, the coastal waters and the sea area you need for fishing with rods no fishing permit. In the coastal waters there is a limitation of (maximum) two fishing rods. Fishing with a bob or smelt rig is in the coastal water also free, provided that the fishing law is rested with the state. If someone else owns the fishing law than a permit for bob or smelt rig is obliged.
You could buy fishing maps of the aquatic sports areas in local tourist offices. You could find a lot of useful information about sports fishing in these.
Here you will find a comprehensive overview of all fishing locations: http://www.visplanner.nl/