Captain vs waterman

Captain

noun
  • The title for someone who holds the captain job on a ship or other vessel. 

  • An army officer title in most countries 

waterman

noun
  • A man who lives or works on the water; a boatman. 

  • Someone who distributes or supplies water for a living; a water-carrier. 

  • A man skilled in multiple aquatic sports disciplines, such as surfing, bodysurfing, undersea diving, canoe paddling, fishing, etc. 

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