Ofu Beach is three kilometres of empty white sand in American Samoa, under the blade of Sunu'itao Peak. The reef in front of it survives water hot enough to kill coral almost anywhere else. The reef crest walls off a line of pools at low tide, leaving barely a metre of water to bake in the sun. The corals in them answer that heat two ways at once. They acclimatise within days, switching gene activity on the fly, and they also carry inherited tolerance built from hundreds of genes. In standardised heat tests they survived at markedly higher rates than corals from the cooler pool next door. Restoration projects elsewhere now look to Ofu stock.
You swim flat over those pools with your fins held still, because most are no deeper than your chest and the coral sits close enough beneath you that a dropped knee lands on something alive. Once you stop kicking the reef turns loud: fish working the rock, and the surf breaking on the crest a few metres out. From the rocky ground at the western end the full three-kilometre curve opens up, with Olosega's green wall closing the view beyond the strait. That strait is only 137 metres of shallow reef, and for generations the way across was to time the tide and walk it, hauling children and cargo. A single-lane bridge went up in 1970, and the old crossing is still there underneath as a pale band. Behind the beach a steep, humid jeep track switchbacks through rainforest to about 490 metres on Tumu Mountain, where the reef flats spread below in bands of turquoise. There is no resort here, no beach bar, nothing to rent. The park that protects all of it owns none of it. In Samoa land belongs to extended families and cannot be sold to a government, so when Congress created the park in 1988 the Park Service negotiated a fifty-year lease with eight villages instead. They keep ownership and their customary rights, and the rangers you meet are largely local.