noun (n)

• submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts(noun.plant)

  Synonym:
  eelgrass, grass wrack, zostera marina
  

  source: wordnet30
• growth of marine vegetation especially of the large forms such as rockweeds and kelp(noun.animal)

  Synonym:
  wrack
  

  source: wordnet30