mooring buoy
structure used to keep one end of a mooring cable or chain on the water's surface so that to can tie on to it.
en-GB/ˈmʊəɹɪŋ ˈbɔɪ/
en-US/ˈmʊɹɪŋ ˈbui/
structure used to keep one end of a mooring cable or chain on the water's surface so that to can tie on to it.