Run the black-sand beaches just south of Whanganui in the Manawatu-Whanganui region. It's a popular and fun day trip, with a great drive down the length of the beach and open dune and shrubland areas to play in at the southern end - the dunes here are pretty amazing. The sand is soft in places, so carry recovery gear and travel with company. Keep a close eye on the tides, as they can rise and block your return route along the beach. If you do get caught out, there's an alternative gravel exit heading inland through the pines from near a gas station, which leads out by Kaitoke prison. The beach is a known fishing spot, with snapper caught on long lines. Note that the surrounding forest is private and has active logging operations, so stay out of the forest blocks - the side tracks in there are also overgrown and scratchy.