ocean vs salt water

ocean

noun
  • Water belonging to an ocean. 

  • An immense expanse; any vast space or quantity without apparent limits. 

  • One of the large bodies of water separating the continents. 

  • A blue colour, like that of the ocean (also called ocean blue). 

salt water

noun
  • any water containing dissolved salt; brine 

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