Show characters in a moment of stillness. As they observe the scene, actions are subtle. The tone can range from relaxed to terrifying.
Example from Literature
I decided to call to him. Miss Baker had mentioned him at dinner, and that would do for an introduction. But I didn’t call to him for he gave a sudden intimation that he was content to be alone—he stretched out his arms toward the dark water in a curious way, and far as I was from him I could have sworn he was trembling. Involuntarily I glanced seaward—and distinguished nothing except a single green light, minute and far away, that might have been the end of a dock. When I looked once more for Gatsby he had vanished, and I was alone again in the unquiet darkness.— F. Scott Fitzgerald, The Great Gatsby