On the north coastline of Okinoerabu island, the repeated battering by the swell and resulting erosion of the coralline limestone reefs is responsible for a curious natural phenomenon. The water that surges into the Fūcha blowhole puts the air inside the cave under pressure, causing it to shoot up through the opening in the top like a geyser. This jet of sea spray is even more impressive during the typhoon period, when it can reach up to 70m in height.