Grohot River

George,I like the composition and your idea for long exposure to achieve smoky water but is something that looking more carefully disturb a bit imo.From foreground to bg the image need more sharpness,I think for sure at 4s exposure time you used a tripod(or a fix position),right smoky water is almost to limit of bright.Looking at f18 you used I think that maybe is too much,you must check if lens you have has maximum sharpness at this value,is very useful for this photozone.de(lot of very good lens tests) or dpreview.I try myself lot of this kind of shots and is not easy to have all elements as we wish.Very useful is for this kind of photo and day moment is ND filter.Maybe you saw just now photos did by Jaun Pavon here on PN,if not have a look on his portfolio to have an idea about.

Hope my opinion is ok to you,my best regards and excellent moments to be for nice photos.

good composition