Rescue buoy (submarine)

Not to be confused with Rescue buoy.
Rescue buoy of the Swedish submarine HSwMS Nordkaparen
Iranian Navy Kilo-class submarine. The rescue buoy (red and white sectors) is just forward of the aft rescue hatch (white ring)

A submarine rescue buoy is a floating buoy, attached to a submarine and released in the event of a serious accident or sinking. The buoy remains attached to the submarine by a cable. Once on the surface it can indicate to rescuers the position of the submarine, and may include a telephone for communication with the trapped submariners.