body of water vs seawater

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. 

seawater

noun
  • The saltwater of a sea or ocean. 

adj
  • Associated in some way with seawater, or intended for dealing with seawater. 

  • Consisting of seawater. 

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