In the Caldera mine, I can not finish this one quest given by a ghost/lich/whatever it is because I have to swim down to a chest...but there is a mysterious lack of water. As a result, I can not swim back up to the top. Is it caused by a mod? Which one...and how do I print my mod list on here?

Just looked in the CS. The interior cell "Caldera Mine" doesn't have water.

And I don't recall any vanilla quests that have to do with ghosts and the Caldera mine.
This is definitely from a mod, so you should post your Load Order so that we know which mods you're using.

If you have Wrye Mash or Mlox, they can produce a text based list of your Load Oder for you.
Otherwise, just copy/paste the list of mods at the bottom of your ini file.

From the sound of it, he's doing the Gnisis Eggmine quest where he has to swim down and get the axe the orc used to murder the miner, not Caldera.

Though why there's no water is strange indeed.

Well, sorry for not being much helpful, but if all else fails, TCL yourself back up. :shrug: