What do I have to do, I need this quest to go on. How can I solve it if rocks spawned under the ground? I cleared the whole area at the waterfall, also the rocks on top of the waterfall and inside the water, nothing there anymore, but I still see at the waterfall a rock, that I can not remove and although I got a blue healthbar of a rock I can't hit anything there. The quest just does not get done. What can I do?
https://steamuserimages-a.akamaihd.net/ugc/2147712396181272399/E5FCE752B981C2A5CE08634B89545898796D288D/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

https://steamuserimages-a.akamaihd.net/ugc/2147712396181309217/96EC43BADE78F38188C1F2B9A7A9B7E23E348D53/?imw=5000&imh=5000&ima=fit&impolicy=Letterbox&imcolor=%23000000&letterbox=false

Problem solved: Obviously the quest just did not show that it was done although it was.