American Samoa

American Samoa sits on the southern edge of the tropical Pacific and contains one of the United States' most biodiverse marine protected areas. The National Marine Sanctuary of American Samoa encompasses Fagatele Bay — a sunken volcanic crater on Tutuila — plus remote Rose Atoll and the Manu'a Islands. Coral coverage is exceptional by Pacific standards, with documented spawning aggregations that researchers track annually. Endemic species include the Samoan damselfish and several undescribed invertebrates. Giant clams up to a metre across are common on shallow terraces. The deep reef drops sharply from the crater rim at Fagatele, offering wall dives to 40 metres alongside prolific reef fish biomass. Visibility is consistently 25 to 35 metres outside of spawning periods.