ok, there's a LOT to unpack here.
so first off, if all you have is video footage of the ocean and sky and the camera moves...that's as realistic as it can be. if you've got 2 stills and you want to be able to perceive parts of the sky and ocean to be nearer and farther away then what you want is called parallax.
there's a couple ways to get this.
if what you have is a single photo, or perhaps several photos stitched together, then there's 2 ways I go about this. if you want the camera to move forwards or backwards, I suggest splitting the sky and ocean into seperate layers, rotate them on their x access untill they're pointing at the camera, and then animate the camera on the z access. this'll looks sorta like you're flying through space. it'll have issues but it'll get you close.
another way is to use mesh warp. I reduce my columns to 1 and rows to 2 and select only the points in the corner of the image. then you animate them EVERY SO SLOWLY from left to right or vice versa. this makes it feel like you're drifting from right to left. if you're getting weird cropping on the edges just use Detail Preserve Upscale to increase the size of the image until you don't see that any more. either that or start w/ an image larger than the final you want and then drop that comp into a new comp the size you want for final render.
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.