Keely posted similar photo in her Instagram in past (she deleted it)
You are right, it is a pic from the same day as this shoot. She must have had to take it down for copyright reasons or because the official pictures hadn't been released yet. Here is the pic she posted ...
Found this on Vimeo from the production team that shot the BTS of the Hackett shoot. The Hackett snippets start at 0:08 and only last a few seconds. As you will see, they actually shot on a real yacht out in the middle of the water. So that should settle the background photoshop question (although there's no way to tell if they might have touched up the background a little).
I never said the yacht was photoshopped. It's just the background on some of them seems to be added later. Body/yacht contour is too defined, too much in contrast with the background, the hair is too perfect - not a single stray hair in sight. And in the photo with the scarf over PB's neck and coast line in the background the background has slightly different feel. I don't know how to explain it - not because it's out of focus,but it looks like it was taken in a different light and adjusted to match the rest of the photo. It's just my take, of course.
I do see what you mean. With the sophistication of photoshop programs and artists who really know what they're doing, I don't doubt that there are parts of the shoot that have some touch-ups to them. Perhaps they mixed and matched backgrounds to fit the mood they were trying to create.