body of water vs light-water

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. 

light-water

noun
  • Normal water, as opposed to heavy water. 

  • Fire fighting foam. 

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