I have seen several other similar moving water ripple photos that have less contrast and are darker and less interesting to my eye. I understand that if there are a lot of similar photos that this reason might be given, but there aren't a whole lot like this that I found. Is there something I am missing? What could I do to improve my chances of being accepted?
The upper and lower section of the image is blurred. It also gives the impression of special effect added, or too much saturation. It doesn't appear natural.
Perhaps you haven't found a lot of these types of images is because buyers don't really need this sort of thing.
It's not very eye catching, I think, hence the aesthetics rejection. You have no focal point. Composition plays a big role in these types of shots.
Take this as a learning curve and an example of what not to submit.