Glass buoys are fist-sized hollow glass balls that were traditionally used by fishermen to keep nets and lines afloat. As of 2014, they have been largely replaced by floats made from aluminum, plastic or Styrofoam; however, in some locations, primarily in southern Japan, glass buoys are still in use.
Because of their delicate appearance and bright, variable colors, antique glass buoys have become a collector's item among non-fishers. These collectors have catalogued buoys in dozens of different shapes, sizes and colors, with stamps indicating they were manufactured in Korea, Norway and Great Britain. Glass buoys are still produced as of 2014, but they are primarily intended for decoration rather than practical use.