body of water vs estuary

body of water

noun
  • Any significant accumulation of water, usually covering the Earth or another planet, such as an ocean, a river, lake or a bay. 

  • Used other than figuratively or idiomatically: see body, of, water. 

estuary

noun
  • An ocean inlet also fed by fresh river water. 

  • A coastal water body where ocean tides and river water merge, resulting in a brackish water zone. 

How often have the words body of water and estuary occurred in a corpus of books? (source: Google Ngram Viewer )