Submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts WordNet 3.0 & Open English WordNet

Zostera marina is a flowering vascular plant species as one of many kinds of seagrass, with this species known primarily by the English name of eelgrass with seawrack much less used, and refers to the plant after breaking loose from the submerged wetland soil, and drifting free with ocean current and waves to a coast seashore. Wikipedia

Species of plant Wikidata

Especially Zostera marina, growing abundantly in shallow bays along the North Atlantic coast. Wiktionary

Zostera marina. Wiktionary (translation)