Abstract: A system is disclosed for detecting, locating and monitoring floating objects and other subject matter at sea on another body of water or in other location of difficult access. A floating unit contains several retroreflecting elements and is placed at a location where detection is desired. For example, rescue or monitoring can be facilitated by detecting the floating unit from the air. Detection may include air borne signal apparatus such as a scanning laser beam or ordinary light source and air borne detection apparatus for detecting and analyzing a reflected signal.