A coral atoll comprising ca.213 ha of land, including the enclosed central lagoon, and 2390 ha hectares of surrounding coral reef and sea. When first listed, the centre of the atoll contained a single tidal lagoon with a narrow connection to the Indian Ocean, but natural processes have since closed this connection. The site is significant for the number of seabirds it supports, including large breeding colonies of red-footed booby (Sula sula) and lesser frigatebirds (Fregata ariel). An endemic species of buff-banded rail (Gallirallus philippensis andrewsi) is a resident within the Ramsar Site. Fish and marine invertebrate fauna are abundant and, while there are few endemic species present, the fish fauna is considered unique due to the mixing of Indian and Pacific Ocean species which are at the edge of their distributions. The Ramsar Site was extended to conform to the National Park boundaries in 2011.