Réunion South Coast

The southern coast of Réunion is the youngest part of the island — built and continuously shaped by Piton de la Fournaise, one of the world's most active volcanoes. Lava flows reach the ocean here with regularity; the spectacle of molten rock entering the sea has been witnessed in at least fifteen eruptions in the past two decades. The coastline at Saint-Philippe and Grand Brûlé is consequently black, sharp, and inhospitable to bathers — the wave energy that hits this exposed coast is Atlantic-magnitude Indian Ocean swell, and the rocky platform is slippery with algae at any tidal state. Spring tidal range at Réunion runs 0.5 to 0.9 m — microtidal. The southern coast is almost entirely without natural harbours; the island's two developed harbours are on the western leeward coast. Diving on the volcanic shelf south and east of Saint-Philippe encounters underwater lava tubes and arches; visibility is variable depending on recent volcanic activity and river runoff. Open-Meteo Marine gridded model, accuracy class ±45 min / ±0.2–0.3 m.