Go to Beachlands which is located in SE Auckland. Take the second view rd, drive till the end, turn right and at the end of that road is a reserve. Park there and walk down steps at end of reserve.
There is a sandspit that connects flat island to beachlands. It's about 200m long and at mid tide there is a brillaint flat water area on the NE facing side. This spot works in any wind except for E - SE.