eelgrass vs aquatic plant

eelgrass and aquatic plant both are nouns.

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

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

eelgrass: submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts
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 hypernyms of eelgrass include hydrophyte, hydrophytic plant, water plant.

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

eelgrass: submerged aquatic plant with ribbonlike leaves; Old World and Australia
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 hypernyms of eelgrass include hydrophyte, hydrophytic plant, water plant.

eelgrass (noun)	aquatic plant (noun)
submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts	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
submerged aquatic plant with ribbonlike leaves; Old World and Australia