I always thought that Oblivion had a really bland and boring underwater environment. Not very populated with fish or predatory creatures, lacking in vegetation and varied underwater terrain, and not enough secret underwater caves, passages, and dungeons. I think, especially since we even have a race with underwater breathing, that the underwater element of Skyrim should be more detailed. I know there are streams now with salmon and the potential for fishing. But I would love to see more realistic looking ponds and lakes. They should be full of life in this game. There should be more hidden underwater artifacts and caves that we can enter and explore, instead of just the odd fingleam and one cave like Oblivion. I would also like the game to include an awesome mythical water monster living underwater as a quest that you have to slay. Maybe an underwater dragon, or something entirely different, like the Loch Ness Monster.
So, what do you guys think!