swamp plant vs water plant

swamp plant and water plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
swamp plant	Yes	No	No	No
water plant	Yes	No	No	No

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

swamp plant: a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath
water plant: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth

Other hypernyms of swamp plant include aquatic plant, hydrophyte, hydrophytic plant.

swamp plant (noun)	water plant (noun)
a semiaquatic plant that grows in soft wet land; most are monocots: sedge, sphagnum, grasses, cattails, etc; possibly heath	a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth