Wangapoua is the car park for New Chum's Beach, sitting on Mangakahia Rd at Whangaehu, Whanganui, and it's clearly popular with beachgoers — 4.8 from 96 Google reviews.
A beach car park out in farm country does a quiet, useful job: firm all-weather ground set back from the soft sand, room to swing a boat trailer around, and a clear track down to the water. Places like this rarely have bins, toilets or water, so regulars arrive self-sufficient and take their rubbish home. It pays to check the tide if you're planning a long walk on the sand, and to take the last gravel stretch slowly, keeping an eye out for stock trucks and tractors. On fine summer weekends, early arrivals get the easy parks.
For a day at New Chum's from Whangaehu or Whanganui, this well-reviewed car park is the natural place to start.