Diamond Head is such an underrated spot with heaps to do in the surrounding area. If you have a 4WD, you can drive onto the beach and set up for the day - with the surf right at your doorstep. If you have a 2wd, you can park in the nearby carpark and walk to the beach. The campsite nearby is also stunning, with heaps of kangaroos gallivanting around. We hosted a girls' trip here and it was SO FUN and social! The campsite is awesome if you can share it with friends.
We also did the nearby short hike up to the top of the headland (see nearby pin) for sunset which rewarded us with breathtaking panoramic views of the coastline and surrounding national park.
The beach itself is 5.5km - so if you're in a 4WD, it's pretty secluded.
I was camping in a 79 Series Landcruiser, as seen in the photos.