I'm a complete beginner at After Effects, what I really need to figure out is:
I have a picture of the ocean, the horizon and the sky.
How can I make a ripple effect in only the water, and a different effect in only the sky?
I cannot figure out how to edit and apply effects to different portions of a single photo independantly. Need help, thanks!
There are many ways to do this. Here is a brief description of one way:
Duplicate the layer a few times and then draw masks on each duplicate to separate the image into pieces: one for the water, one for sky, etc. Then apply appropriate effects to each duplicate layer.
That's all there is to it.
Yes, I know that that was very brief, without much detail. If you know the basics of After Effects already, then what I just said should be enough detail; if you don't know After Effects already, then you need to learn the basics before you try to tackle any real project.
I strongly recommend that you work your way through the basics here:
Just so that you can see what you're working toward, here are a couple of videos that show variations on what I just described for applying an effect only to a specific moving part of a scene: