fresh water vs saltwater

fresh water

noun
  • Water with a very low content of dissolved salt, as opposed to brackish water or salt water. 

saltwater

adj
  • New Keynesian or Keynesian, in reference to macroeconomics and economics departments on the East Coast and West Coast of the United States of America. 

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