The curve of the shoreTrace the waterline with a finger on the map. The point where it turns sharply is often easier to recognize from a distance than the highest hill.
Ridges in layersLook across the bay before looking down. The nearest slope usually has the clearest outline. Farther ridges fade until their edges almost match the sky.
A line left by the tideA thread of dry kelp can mark an earlier reach of the water. Sketch its shape beside the wet edge of the sand and watch how the distance between them changes.