Hydrothermal crack

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A Hydrothermal crack is the entrance to the Underwater World and can be found randomly in the Sandy biome.

Each entrance leads to the first level of the Underwater world, called Reef. When first discovered, the Cracks will be closed and they will appear as a single fissure which can be mined only with an Opulent Pickaxe. After being mined, the cracks will be opened and they will reveal a hole leading into the ocean. It takes 4 hits from an Opulent Pickaxe to open the crack.

In a world, 2 hydrothermal cracks can only be found and their number cannot be changed, even in the world settings. Only opened cracks are marked on the map.