#acoustic_buoy  a buoy that can be heard (at night)
  supertype:  #buoy  bright-colored; a float attached by rope to the seabed to mark channels in a harbor or underwater hazards
  subtype:  #bell_buoy__gong_buoy  a buoy with a bell on it
  subtype:  #whistle_buoy__whistlebuoy__whistlingbuoy  a buoy that makes a whistling noise

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