water rat vs sailor

water rat and sailor both are nouns.

Word	Noun	Adjective	Verb	Adverb
water rat	Yes	No	No	No
sailor	Yes	No	No	No

As nouns, sailor is a hypernym of water rat; that is, sailor is a word with a broader meaning than water rat:

Other hypernyms of water rat include crewman.

water rat (noun)	sailor (noun)
any of various amphibious rats	a stiff hat made of straw with a flat crown
common large Eurasian vole	any member of a ship's crew
a person who enjoys being in or on the water	a serviceman in the navy