The wetland area behind Makalawena beach was designated a National Natural Landmark in 1972. The marsh is known as Ōpaeula Pond (Hawaiian for "red shrimp") and was the site of a small fishing village that was wiped out in the 1946 tsunami. The of wetland provide one of the last remaining nesting grounds of the "āeo" (Hawaiian stilt, "Himantopus mexicanus knudseni"), the "alae keokeo" (Hawaiian coot, "Fulica alai"), and the only known breeding area for the "aukuu" (black-crowned night heron, "Nycticorax nycticorax hoactli") in Hawaii. The pond is located at coordinates in the privately owned area between the two sections of the state park.