diver vs water dog

diver

noun
  • Someone who works underwater; a frogman. 

  • Someone who dives, especially as a sport. 

  • The New Zealand sand diver. 

  • A competitor in certain sports who is known to regularly imitate being fouled, with the purpose of getting his/her opponent penalised. 

  • The long-finned sand diver. 

  • loon (bird) 

water dog

noun
  • A retriever type of gun dog bred to flush and retrieve game from water. 

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