Sunlight illuminates a water body, such as a lake, stream, or, ocean, a portion of the light will penetrate the water body while the remainder will be reflected into the atmosphere from the water surface. When viewed from an airplane or from space, the light reflected from the water surface, referred to as "sunglint," will appear as a circular bright area on the water surface in the direction of the Sun. The location and size of the sunglint is a function of the location of the Sun in the sky, the location of the observer, and the roughness of the water surface. If the water surface were perfectly flat, the surface would appear as an image of the solar disk. However, the surface of a natural waterbody is rarely flat. Wind blowing across the water surface produces waves, small waves at first then gradually larger as the wind increases speed and is sustained. The presence of waves tends to disperse the surface-reflected light, and the result is a spreading of the sunglint pattern.

Photographs from space of the ocean sunglint pattern are a valuable tool for studying physical oceanographic and atmospheric processes and other phenomena that affect surface roughness. Variability in windspeed and direction, surface water currents, and water temperature all produce unique signatures within the sunglint pattern. A good example is a man-made oil slick that results from bilge pumping. Viewed form a ship, the slick will appear as a long narrow area of smooth water-the oil tends to damp out small capillary waves. Viewed within the sunglint pattern, the slick will appear very bright near the center of the pattern. Because this area is more mirror-like than the surrounding water, more sunlight will be reflected towards the observer.