query: # Bodies of water that most watercourses end in (transitive).
  # For example, over 4000 watercourses eventually flow into the Ob,
  # and since the Ob flows into the Kara Sea, the Kara Sea has over 4000 results as well.
  SELECT ?mouth (COUNT(?watercourse) AS ?count)
  WHERE
  {
    ?watercourse wdt:P403+ ?mouth.
  }
  GROUP BY ?mouth
  ORDER BY DESC(?count)
  LIMIT 10