eelgrass vs water plant

eelgrass and water plant both are nouns.

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

As nouns, water plant is a hypernym of eelgrass; that is, water 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
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 eelgrass include aquatic plant, hydrophyte, hydrophytic plant.

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

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

eelgrass (noun)	water 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