water snake vs colubrid snake

water snake and colubrid snake both are nouns.

Word	Noun	Adjective	Verb	Adverb
water snake	Yes	No	No	No
colubrid snake	Yes	No	No	No

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

water snake: any of various mostly harmless snakes that live in or near water
colubrid snake: mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes

Other hypernyms of water snake include colubrid.

water snake (noun)	colubrid snake (noun)
any of various mostly harmless snakes that live in or near water	mostly harmless temperate-to-tropical terrestrial or arboreal or aquatic snakes