boater vs shipmate

boater

noun
  • One who works on a boat, especially as captain. 

  • Someone who travels by boat. 

  • A straw hat, very stiff, with a flat brim and crown. 

shipmate

noun
  • A fellow sailor serving on the same ship as another. 

  • Any sailor (when used as a form of address by a sailor). 

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