This is not the James River I know. We have one of those here in Missouri, and your James River is a lot nicer looking (at least the photo makes it nicer looking).
From what kundalini posted, I ask a question. Would it be an okay idea to crop about 1/6th or an 1/8th of the bottom of the photo out? That way, the rock issue is gone and your horizon gets pushed off of center. I am a novice, but it seems that taking care of two problems this would be a positive thing.
The left tree is mildly distracting and does throw off the balance somewhat, but the photo is amazingly well done. I think to a novice, they would hardly care. Now if you're trying to impress someone really advanced photographically, they may see flaws, but I would go as far as to say 99% of the people out there would find this photo spectacular, even as is.
Great choice of shutter speed. I would be afraid to push the blur too far, but it worked! Kudos!