Principles of Design

In this picture...

Balance: there's a balance in this picture because there is something both in the top and the bottom; the lake is what you see in the bottom-ish, and the mountains and trees are what you see in the top.

Proportion: the proportion of this picture is a little hard to judge, but I think you're supposed to use those things that look kinda like ducks (to me) in the middle of the photo, to see that the lake isn't like 2 feet across or something.

Rhythm: I think the water, trees, and mountains are what gives this photo rhythm. The water is all the same, the trees look the same, and you could imagine that this scene could go on all up and down this river, or lake, or whatever it is.

Emphasis: the blue thing in the background is the "break in the unity" for me. It looks like an old car, or building maybe, and is the only thing that seems out of place in the picture.

Unity: this picture is of a lake with a jungle, so the fact that everything is green and living and jungle-y is the unity in this picture.