[Raktizz Nemmex]

Well, all the underwater tunnels lead to other places all of which I've been, but there's one place where you have to levitate up to and its a small ledge only big enough to stand on, then its all blocked off by blocks, but there are cracks in it so I can see far enough to see another doorway, but with no way to get through.
And the Cavern of Dubdilla is on the East Coast and is the Grazelands area, not to sure of any landmarks really close to it, but it shouldn't be too hard to find. If you've become a vampire and want to un-vampire yourself, you need to do a quest in here for a Daedric god, not sure which one though.

Raktizz