I've been mulling this one over for a while.
I like your choice of shutter speed to get the silky water.
I agree that the horizon needs to be leveled.
A simple way to do this is with the measure tool in Photoshop.
Use the tool to draw a line across the edge of the water, then go Image> Rotate Canvas> Arbitrary. Then click OK.
I would also recommend eliminating the distractions that are sticking out of the bottom (blades of grass and such) by either cropping higher or patching them in Photoshop.
Some of the greens are a bit over-saturated and even appear to "glow." If that is the look you want, then great, but you should boost the rest of the areas to match. Or you could try to do an Orton type effect on the whole picture. That might look real nice.
Hope this helps,
jim