I know they're not the terrors they were in Morrowind (less so in Oblivion), but I still wanna be able to kill slaughterfish when I'm submerged and/or they're not swimming shallow. You can't "unsheathe" spells or weapons while underwater, but I have shot some with arrows while wading/standing on shore. I heard the ebony mail effect works, so flame cloak,etc. spells might work also. Any other known or possible methods? Still hate the little crocodile mosquitos almost as much as cliff racers!

Speaking of which, how do you kill horkers? I know, they're (giant) sitting (stumbling) ducks on dry land, feel sorry for 'em, but underwater? And are these the only 2 aquatic creatures? If not, what are the others, and how do you kill them?

Unfortunately, Beth forgot to give us harpoons! =p I just lure slaughterfish towards shore and then kill them. Or bring a follower, they can usually kill them with arrows and destruction spells standing on shore. I think they have better aim/sight to locate the fish in the murky waters LOL

And Horkers? They just sit on land anyway, you kill them like anything else.

There are mudcrabs, but they are usually along the shore line, so you can kill them easily like anything else.

Then there are fish you use for alchemy purposes, but those you don't have to kill, you just collect them like you would flowers and grass and stuff.

"Crocodile Mosquito"? LMAO!!!!!!!!!!!!

Apparently the OP hasn't had the misfortune of encountering the Weresharks yet... oh the horrors...

Also, there's Pierre the Werecow... deceptively docile looking, don't be fooled.

Other aquatic creatures? I take it that means you have not encountered any "aquagoats" yet?

http://www.youtube.com/watch?v=MBtH1T5FfU4

Aura Whisper + well-aimed arrow

Wade in a bit and lure them back to shore

Bump.

though not really a problem for me the lack of aquatic enemies/combat and further lack of submerged areas to raid in skyrim saddens me

get on to the shore and cast magic, shouts or shoot arrows at them. There are no other hostile aquatic animals.(maybe mudcrabs?)

One of my character used the bow along with the Steady Hands perk, which allows you to slow down time. Or use the slow down time shout and try killing it with and arrow. I recommend luring it to the surface.

I've seen rabbits underwater. Just imagine how hard those are to kill.

Ice Form shout hurts them and makes them float to surface.

Frenzy's a good one too, if theirs a bunch.

I usually use Fire Breath - gets 'em a fair way out into deeper water even.

If you're a mage, the destruction cloak spells work well.