water plant vs aquatic plant

water plant and aquatic plant both are nouns.

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

As nouns, water plant and aquatic plant are synonyms defined as:

water plant and aquatic 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 synonyms of water plant include hydrophyte, hydrophytic plant.

water plant (noun)	aquatic 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	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