Kualoa Regional Park on the northern part of windward (eastern) Oahu: drab name, very cool place. The camping area of the park has an excellent swimming beach, including a short walk to the sands of Secret Island—which only seems like an island since its hemmed in by the bay on one side and big Moli'i Fishpond on the other.
You may recognize the jagged ridge that lords over the scene, featured in TV commercials and programs (Five-O) and movies (Godzilla, 50 First Dates, Jurassic Park, Mighty Joe Young).
Calm waters attract outrigger canoeists. Just off the point is a small island (you can also swim to it) called Mokoli'i, but known as Chinaman's Hat (its profile looks like one of the straw hats worn by Chinese workers in the old days).
Kualoa Ranch, on the mountain side of the rural highway from the beach park, has several historical sites dating from the sugar cane heydays in the late 1800s.