Its a Harsh "Karst" World!
"Karst Topography is a landscape shaped by the dissolution of a layer or layers of soluable bedrock usually carbonate rock such as Limestone or Dolomite.
Due to subterranean drainage, there may be very limited surface water, even to the absence of all rivers and lakes. Many karst regions display distinctive surface features, with sinkholes or dolines being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris, or confined by a superimposed non-soluble rock strata. Some karst regions include thousands of caves, even though evidence of caves that are big enough for human exploration is not a required characteristic of karst.
Various karst landforms have been found on all 6 major continents". .... Wikipedia
You do not have to go down into the cracks to retrieve the cache.