sea-puss vs undertide

sea-puss and undertide both are nouns.

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

As nouns, undertide is a hypernym of sea-puss; that is, undertide is a word with a broader meaning than sea-puss:

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

Other hypernyms of sea-puss include undercurrent.

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