Fluorescence is another light-producing phenomenon used by many marine organisms. Unlike its optical “cousin,” fluorescence happens when a fraction of the light that is illuminating the organism is absorbed and then re-emitted as a different color. For example, when you shine an ultraviolet (UV) light on a blacklight poster and it glows, that is “fluorescence” as it is driven by the input of light. Scientists think that fluorescence in marine animals living in the upper-to-middle part of the water column may play a specific function, such as attracting prey or providing visual recognition.