water plant vs vascular plant

water plant and vascular plant both are nouns.

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

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

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
vascular plant: green plant having a vascular system: ferns, gymnosperms, angiosperms

Other hypernyms of water plant include tracheophyte.

water plant (noun)	vascular plant (noun)
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	green plant having a vascular system: ferns, gymnosperms, angiosperms