Kauapea Beach, also known as Secret Beach, is a secluded beach that can only be accessed via hiking trails, which is why it is less frequented by tourists. It is the perfect spot to visit after a rain storm, as the waterfalls by the lava formations are at there strongest at this time. You'll most likely want to ask a local how to get to the waterfalls, as there is a small unmarked boot path located near a neighborhood in Kilauea. It is definitely worth the adventure.
Disclaimer - as I was shown this spot by a local, I would suggest asking for the exact location of the trail from a local. It can be reached by one of the nearby neighborhood roads in Kilauea.
The boot path is fairly short (approximately a mile or so), and involves a short stream crossing, which can be a bit tricky if there have been any recent rain storms. The lava formations are located to the North of the actual beach, from which the Kilauea lighthouse can be seen. From what I heard, there's normally only a couple waterfalls flowing, but if there's been rain recently there can be as many as four waterfalls, which was the case when I went.