On a recent visit to Holland I found that you are given NS Day Tickets which give 24 hours unlimited travel in Holland on the day you check in at the station.
This means you don't have to use them solely for travelling to or from Hoek van Holland, but can be used for longer journeys during your stay in the Netherlands.
This means you don't have to use them solely for travelling to or from Hoek van Holland, but can be used for longer journeys during your stay in the Netherlands.