In Zereth Mortis, you have to interact with this object to unlock a chest for the Sand, Sand Everywhere achievement. I’m standing where the orb is and I don’t see it, but I’ve seen two players so far interact with it and get the needed buff. I’ve seen other players reporting the same problem on WoWhead and no solution has been suggested. I tried disabling all addons and that didn’t work. I tried logging out and logging in and that didn’t fix it either.
Don’t see the reports that you claim. Check the videos out in the comments, they might help out.
The comments are here: https://www.wowhead.com/object=369757/submerged-chest#comments
I’ve watched a video. I’m standing where the orb is. I’ve seen two other players interact with it. It is still not visible for me.