salt water vs seaway

salt water

noun
  • any water containing dissolved salt; brine 

seaway

noun
  • An inland waterway used by seagoing shipping. 

  • The headway of a vessel. 

  • A lane or route at sea that is regularly used by ships; a sea lane or trade route. 

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