Goat island beach is a marine reserve (note this means no dogs or fishing etc) located north east of Auckland . This is one of the very top spots to snorkel in NZ and you can do it for free if you have your own gear! Other activities including the glass bottom boat and glass kayaks are offered here.
The campground is located a bout a 15minute walk from the beach or a minutes drive. The grounds let you camp anywhere or the large lawn for $20 a night. Hot showers, cutlery/utensils, plates/bowls and cooking equipment are also supplied however when I have been here previously the dishes were not done, microwave and kettle we’re filthy so I would recommend bringing your own gear or camping somewhere and driving a bit further to the marine reserve.
Other things you can do in this area are eat at Leigh Fisheries, visit Matheson bay, surf/swim at Parkiri, pop down to Matakana, and plenty more.