intertidal zone vs seaboard

intertidal zone

noun
  • The part of a shore between high water and low water, especially the beach exposed at maximum ebb spring tides. 

seaboard

noun
  • The area bordering the sea; a coastline; a sealine. 

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