I know. So Cheesey! But the romantic silhouette in the sunset photos will always be around, until the end of time. As simple as it seems, a lot of compositional issues come up. For you avid readers, you will note right away the selectively tilted horizon. Also, the dark shadow of the couple is in front of the part of the ocean that most brightly reflects the sun, for maximum contrast.
And one other thing to take note of, especially if you're a tall photographer. Don't put the horizon directly on top of anyone's head! I have many photos of me, taken by a certain taller person, who at normal camera holding height, by default places the horizon exactly on top of my head. It looks awkward. And certainly don't put the top of the person's head UNDER the horizon. In general, for a flattering photo of a shorter person, tall people ought to squat down a little, so they're not pointing a camera down at their midget subject - otherwise, not only would one then photograph a lot of floor, but the short person's head looks big. If you're photographing puppies and toddlers and intentionally making cute big heads, that's OK. But it's a different story if you are using a portrait lens (as opposed to wide angle, which is what most point and shoots have). No I don't have height issues.
Back to horizons, I think it's best for the horizon not to cut through major joints, like the neck or knees. I suppose waist would be OK. Chest height is a good cut through point.