I recently started a new hardcore world. The first thing I always do in a new world is chop some wood; wood is the essence of Minecraft survival. I noticed a pool of water nearby, which had a single line of water blocks that were raised above the others, without any runoff to the rest of the pond. Odd, I thought, and then I continued chopping.
Just as I was breaking through the second block of wood from a random tree trunk, a white “ghost” filled my screen, screamed at me, and died. Nothing else; it didn’t attack me, move around, etc.
I was kinda spooked (for good reason), and I ran around the tree and the surrounding area in search for more ghosts. None to be found.
So, I returned to my tree and resumed my chopping. Except I didn’t. I quickly discovered I could no longer destroy blocks of any kind.
The moral of the story: stay away from glitchy pools of water. They indicate an unusual presence of apparitions, specters, and other haunts, which will render you utterly useless in hardcore worlds.