WOW Quest:A Short Fuse (13263)  

After you fall down into the hole, the Crystal you need to talk to is under water (it is very small). This then leads to talking with the ghost of human boy down there to get the next quest (Time to Hide) which requires you to kill the Faceless Lurkers until you receive 3 blood samples. Once that is complete take the portal back to the surface and finish (Return to the Surface) at the ship - Orgrim's Hammer.