boating vs merchant marine

boating

noun
  • The activity of going out onto a body of water in a boat. 

  • In Persia, a punishment of capital offenders, by laying them on the back in a covered boat, where they are left to perish. 

merchant marine

noun
  • A ship dedicated to commercial, rather than military, purposes. 

  • Synonym of merchant navy. The fleet considered as an entire combined force. 

How often have the words boating and merchant marine occurred in a corpus of books? (source: Google Ngram Viewer )