#reef  a submerged ridge of rock or coral near the surface of the water
  supertype:  #ridge  a long narrow natural elevation or striation
  subtype:  #coral_reef__coralreef  a reef consisting of coral consolidated into limestone
     subtype:  #atoll  an island consisting of a circular coral reef surrounding a lagoon
        instance:  #Kwajalein  #Eniwetok.atoll__eniwetok  #Kwajalein.atoll__kwajalein  #Midway_Islands
     subtype:  #barrier_reef__barrierreef  a long coral reef near and parallel to the shore
     subtype:  #Florida_keys__key__cay  a coral reef off the southern coast of Florida

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