EDIT the following refers to the original image in the original post
I can't imagine this image, as posted, will ever work. The replace sky algorithm has to have some criteria for determining "sky", "horizon" and "foreground", and this image falls way outside. What to do with the water?
Yes, I know that AI-algorithms are trained on a large number of real world images, but the argument is the same. There has to be someting in thepixels that separate sky and land in a meaningful way.
Put another way: if it worked here, it would be less effective on "standard" images, because the criteria would have to be diluted and inflated.
I just wouldn't expect this to work to begin with.