A ground swell, a broad deep undulation of the ocean, is often caused by a far-off storm. Its waves felt even under clear skies. Causing here, in Edward Hopper’s painting, a buoy to sound-off, even when there is no apparent danger. The four figures on the passing catboat, three men half-dressed in white and a woman in red, sail a white boat over the white swells and under a bright sky. In this quiet and voyeuristic view, the figures aboard the boat are disengaged from each other. Their gazes fixed on the black bell buoy, and their trancelike state is reinforced by the rolling waves beneath them. Counterpoint to all of this lightness is the buoy itself and the darker swells on the horizon. Painted in September of 1939, the picture’s symbolism is unmistakably linked to the advent of World War II. Hopper and his wife were living at a beach house that they built themselves, in South Truro, Massachusetts, when he painted “Ground Swell”, which is now housed at the National Gallery.