#estuary  the wide part of a river where it nears the sea; fresh and salt water mix
  supertype:  body_of_water__water  the part of the earth's surface covered with water (such as a river or lake or ocean); "they invaded our territorial waters"; "they were sitting by the water's edge"
  subtype:  firth  Para_River
  instance:  Rio_de_la_Plata
  part of:  river  a large natural stream of water (larger than a creek); "the river was navigable for 50 miles"
     part of:  water_system__watersystem  a river and all of its tributaries

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