A third method is to include the near shore as well as the farther shore. Also, try shooting straight across a body of water, instead of up or down it. Shoot from angles where there is no major change in distance between the left side of the frame and the right.
Sweeping curves, lines from the edges, joining the shore at points where the mind can easily realize that the shore is not supposed to appear level are all good ways to watch your horizon. There are more ways, so take your camera and find some of them. Play with objects that the mind should think of as level or plumb, and see how incorporating them into your images affects your horizon.
Many of these same tricks and effects can also be noticed with fields, some skylines, and other open spaces. Play around, enjoy. Try to take notes of which pictures you take level, and which ones are offset so that you can understand what leads to acceptable results, and what keeps you scrathcing your head trying to figure out what is wrong.