sea creature vs creature

sea creature and creature both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea creature	Yes	No	No	No
creature	Yes	No	No	No

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

sea creature: any of numerous animals inhabiting the sea including e.g. fishes and molluscs and many mammals
creature: a living organism characterized by voluntary movement

Other hypernyms of sea creature include animal, animate being, beast, brute, fauna.

sea creature (noun)	creature (noun)
any of numerous animals inhabiting the sea including e.g. fishes and molluscs and many mammals	a living organism characterized by voluntary movement
	a living being
	a person who is controlled by others and is used to perform unpleasant or dishonest tasks for someone else