Ofu Beach fronts a reef that ought to be dead. In the shallow pools a few steps off its sand, the water climbs to 35°C on a still afternoon and can swing 6°C in a day — heat that bleaches and kills coral almost everywhere else. The staghorn and table corals here live through it, and Stanford biologists have spent years here working out how, making this beach a reference site for heat-tolerant coral. Two miles of white sand curve along the south shore of Ofu, a Samoan island of a few hundred people: the spire of Sunu'itao, the eroded core of an old volcanic dike, stands at the far end, Tumu Mountain's forested ridge rises to about 490 metres behind, and across the Asaga Strait the green wall of Olosega climbs to 629 metres. All of it lies inside the National Park of American Samoa — the only US national park south of the equator, its land leased from the villages rather than bought.
You wade in straight from the beach, no boat and no dive shop, and the coral begins within a few strokes: staghorn thickets, giant clams, parrotfish grinding at the reef — a fraction of the roughly 250 coral and 950 fish species the park protects. Getting here is what keeps it this way. Samoa Airways flies to the Manu'a Islands twice a week when weather allows, the last leg is often a boat, and the lodge by the airstrip is the only place to stay; there are no restaurants, no medical care, and an evacuation can take days. The sand is usually empty; the park sees a few thousand visitors a year. After dark the peaks turn to silhouettes under a sky with no city glow near it, and from September humpback whales come into these waters to calve.