A single Porites coral head roughly 10m across and 10m high, the largest known coral colony in the world, estimated at over a…A single Porites coral head roughly 10m across and 10m high, the largest known coral colony in the world, estimated at over a thousand years old, standing alone on the slope like a boulder. Typhoon Nepartak knocked it off its base in 2016 and it was propped and re-secured; it is still growing. Green Island was a political prison through Taiwan's martial-law decades, and the Oasis Villa where dissidents were held is now a human-rights memorial a short ride from the dive sites. The island also has Zhaori, one of only a handful of seawater hot springs in the world, which you sit in at dawn. Anchorage: Green Island's harbours are small and swell-prone; most visitors come by ferry from Taitung. Hazards: The Kuroshio runs hard past the island; this is a drift dive with a boat pickup. Altro