Oh this reminds me of Cixin Liu's (of the Three Body Problem fame) short scifi Mountain. It describes an alien species that lives in the mantle of a planet. Th

Oh this reminds me of Cixin Liu's (of the Three Body Problem fame) short scifi Mountain. It describes an alien species that lives in the mantle of a planet. Their explorer finally dug through to the crust, when they were met with never before seen liquid water that instantly kills them as well as their (non water proof) equipments. Fascinating short story.