Abstract: A sensor for the reliable detection of oil spills using fluorescence techniques. An ultraviolet (UV) light source is located around an optical column with which selected wavelengths of fluorescing hydrocarbons or other substances can be detected. The source of UV light is held at a constant level and special techniques are employed to remove background optical noise from the various detected wavelength signals. Short and long term running averages are generated to detect oil spills. A special buoy is employed to allow the sensor to be oriented at a cavity in the buoy to reliable detect oil spills on waterways. The buoy has windows to enable surface water to freely pass through into the cavity while preventing turbulence from open water waves and wind. The buoy has a low center of gravity well below the water line with a large submerged segment to reduce heaving motions and provide a stable platform for the detection of fluorescing substances.