undertide vs sea puss

undertide and sea puss both are nouns.

Word	Noun	Adjective	Verb	Adverb
undertide	Yes	No	No	No
sea puss	Yes	No	No	No

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

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

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

undertide (noun)	sea puss (noun)
a current below the surface of a fluid	the seaward undercurrent created after waves have broken on the shore