Horseshoe Bay is a crescent of pink sand on the south shore of Bermuda, and the pink is an animal. Homotrema is a single-celled creature no bigger than a pinhead that grows in red crusts under the reef's overhangs, and when it dies the waves grind its shell into the white coral sand. Late in the afternoon, once the ebbing tide has left the sand wet and at its deepest colour, you can crouch at the waterline and scoop up a handful. Among the white flecks of coral and shell the blood-red grains show up by eye. The beach is closed at both ends by cliffs of aeolianite: ice-age dunes blown up off the shore and cemented into solid stone. Up close you can read the old dune slopes in the layering. Weathered towers of the same rock rise out of the shallows just offshore, breaking the waves before they reach you and leaving calm pockets behind them.
None of it comes from the volcano underneath. Bermuda is not a coral island but a thin lid of limestone laid over a dead seamount that stopped erupting roughly 30 million years ago. Every cliff, dune and grain of sand here comes from the living skin on top of it. The crowd stops where the main crescent ends. A sandy trail east under the cliffs takes you to Butts Beach, Stonehole Bay and Jobson's Cove within minutes, pockets of the same sand walled in by rock. Where the outcrops almost meet, the sand runs between them in narrow corridors down to the water. Longtails nest in crevices in the cliff above the beach, and they are helpless once they land. Their legs sit so far back that they cannot stand upright, so on rock they shuffle along on the breast, pushing with their wings. Taking sand off a Bermudian beach is illegal and the airport confiscates it, and visitors are still reckoned to carry off about three tonnes a year. The reef replaces it one broken shell at a time.