Superstructure (of a buoy, usually lighted)
Alternative term: Cage (U.S.A.)
That part of the buoy built on top of the body of the buoy and used as a daymark or part thereof and usually to support the light or a topmark or a radar reflector, or a combination of these.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM