sea nymph vs water nymph

sea nymph and water nymph both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea nymph	Yes	No	No	No
water nymph	Yes	No	No	No

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

sea nymph: (Greek mythology) a water nymph who was the daughter of Oceanus or Nereus
water nymph: (Greek mythology) any nymph of the water

sea nymph (noun)	water nymph (noun)
(Greek mythology) a water nymph who was the daughter of Oceanus or Nereus	(Greek mythology) any nymph of the water
	a fairy that inhabits water
	submerged aquatic plant having narrow leaves and small flowers; of fresh or brackish water
	a water lily having large leaves and showy fragrant flowers that float on the water; of temperate and tropical regions