A plume of milky-white water where shallow hydrothermal vents pour sulphur into the sea, staining the ocean turquoise around a…A plume of milky-white water where shallow hydrothermal vents pour sulphur into the sea, staining the ocean turquoise around a black volcanic island. The vents support a population of pale 'sulphur crabs' living in water acidic enough to kill most marine life, and whales and dolphins work the deep water just offshore. Guishan was inhabited until 1977, when the residents were moved ashore and the island became a military zone. It reopened to visitors in 2000 under a permit system. It is one of very few places on earth where you can look at an active submarine volcanic system from the surface. Anchorage: No sheltered anchorage. Guishan is a day objective from Wushi, often combined with whale watching. Hazards: Acidic vent water, sulphur fumes and hot patches at the vents. Nobody swims at the vent mouths. More