undertide vs undertow

undertide and undertow both are nouns.

Word	Noun	Adjective	Verb	Adverb
undertide	Yes	No	No	No
undertow	Yes	No	No	No

As nouns, undertow is a hyponym of undertide; that is, undertow is a word with a more specific, narrower meaning than undertide:

undertide: a current below the surface of a fluid
undertow: the seaward undercurrent created after waves have broken on the shore

Other hyponyms of undertide include sea-poose, sea-purse, sea-puss, sea purse, sea puss.

undertide (noun)	undertow (noun)
a current below the surface of a fluid	the seaward undercurrent created after waves have broken on the shore
	an inclination contrary to the strongest or prevailing feeling