When in Auckland, a visit to Rangitoto Island is definitely a must! I visited the island with Auckland Sea Kayaks who offer a full day guided kayaking trip. I did this trip not so long ago. Most people will decide to go with the ferry which have a few scheduled services per day, but I highly recommend kayaking as an alternative. If you do decide to go with the ferry though, make sure that you take enough fluids and food as there is no place to buy it once on the island.