I like nighteye that way. That's how night vision works in reality, and there needs to be SOME reason to use something like a torch or a light spell over it.
Considering that this is magic we're talking about, I don't think how real life night vision works has any bearing on it, though I suppose giving players a reason to use lights when they could use nighteye might be one reason to have that effect, still, I think Bethesda could do with a better effect. In Oblivion, I generally just didn't bother with nighteye because the effect pretty much ruined the atmosphere of dungeons, and sometimes actually made it harder to see as it made everything the same color, potentially causing some objects to blend into each other, I'm not sure how nighteye should look, or how it will look, but if Bethesda decides to ditch the blue filter, I won't miss it.
As far as underwater effects, while you certainly shouldn't be able to see perfectly clearly underwater, I'd agree that Oblivion made it too merky, it's kind of nice to be able to see SOMETHING while swimming, on the other hand, some mods water mods, I felt, made water too clear. Of the various Oblivion mods that change this, I personally feltr that the one which strikes the best balance between visibility and merkiness, which incidentally was also my favorite Oblivion water mods, out of the ones I had tried, until the release of the recent Liquid Water, was Enhanced Water, the underwater view distance wasn't absurdly long like some water mods, but it was better than the default water. I'd also say that a modern game could do some nice under water effects beyond just applying appropriately colored fog to the screen, but that's a subject for another discussion, I'm just talking about underwater visibility here, not the quality of the water effects themselves.