A device that can provide sustained release of a detectable marker into a surrounding body of water as well as methods of forming the device and methods of using the device. The devices and methods can be utilized to locate people or vessels, e.g., by search and rescue personnel, following the disabling of air or water vessels of any type or size on/in a body of water. The devices include multiple, separated layers that each include a detectable marker, e.g., a fluorescent dye. The dye-containing layers are separated from one another and sequentially released over a predetermined controlled period of time and as such the device can continue to release a detectable marker over an extended period of time into surrounding water.
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