amphibian vs aquatic

amphibian

noun
  • An animal of the Amphibia; any four-legged vertebrate that does not have amniotic eggs, living both on land and in water. 

  • A vehicle which can operate on land and water. See Wikipedia article on "Amphibious aircraft" 

adj
  • Capable of operating on both land and water amphibious. 

  • Of or relating to the class Amphibia. 

aquatic

noun
  • Any aquatic plant. 

adj
  • Relating to water; living in or near water, taking place in water. 

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