How to improve your photo
Not going to insist on the fact you shot with aperture priority hence auto exposure, but still have to mention it... We have been working for some time here and I guess you knew I might say something. I will always insist in full manual, even if the work is already very good.
First thing to point out is the shadow on the background sand half way up. This is not corresponding to any cloud on the sky that would do it, because there is no cloud that could and the Sun is setting. This sort of darker shadow, or the brighter area on the bottom, makes it look unrealistic. I would go back to this and try to do it in a way that you don't have such a difference, maybe keeping it a bit darker on the bottom but adding punch with selective contrast. I do like the fact that the rock is bright as it is. Not easy to make this work perfect, not easy at all.
Second thing, and this is what is giving is a bit of the painterly effect, is the over feathering on the borders of the 'chiaroescuro'. With time and patience, and a lot of attention to detail, you can avoid this manually. I suggest you try and do it to make it look more convincing. I do like the dreamy effect though, which is not exactly a soft lens effect, and some really well produced feathering can help keep it.
Another suggestion is to check if your not creating a bit of ghosting, as we can see specially on the horizon rocks. Looks like there is some kind off fog and the atmospheric conditions here have none of it.
Did you obscure the top after of did you use a neutral density filter? ND filters can make it a hole lot easy for you but they limit the quality you can achieve on the final result. This looks like you could have used one and then tried to work it out after. Also, if you darken it with some sort of gradient mark, it will do the same as a ND filer.
About the sky and it's reflection, you can have a reflection brighter then the sky, but usually this is not possible to witness in a realistic representation, so in here there is a divide on what you are aiming at: illustration or photography. The biggest difference here is that photography, in general, is realistic, but illustration can be not. To have to bottom a bit darker as I have suggested up will solve that.