Thanks a lot for the feedback. I must say that I agree completely. The first one is way too much, and the second got this tasteless glow effect feel to it that really don't fit the overall style. I find that coloring large bodies of water is the part of mapping I have most difficulties with right now: I just can't find the "style" I'm looking for. Even more reason to say how much I appreciated all your input!
From your suggestions I attempted a couple of different styles and came up with these three. Personally, I feel more for the first one, however, I'm more indecisive than ever about this. And if I end up going with the first, I will probably make the color gradient more evident. What do you guys think?