Secret Beach Properly known as Kauapea Beach This is another huge beach, nearly 1 12 miles long with fine white sand, black lava rock, stunning cliff .\rbr\rbrKauapea Beach, popularly known as Secret Beach, is on the north shore of the island of Kauai in Hawaii. The beach is known for its size, seclusion, and .\rbr\rbr\rbr\rbrKauapea Beach, popularly known as Secret Beach, is on the north shore of the island of Kauai in Hawaii. The beach is known for its size, seclusion, and beauty.