hydatoid vs seawater

hydatoid

adj

  • watery, aqueous 

seawater

adj

  • Consisting of seawater. 

  • Associated in some way with seawater, or intended for dealing with seawater. 

noun

  • The saltwater of a sea or ocean. 

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