Neptune Grass
(Posidonia oceanica)

Beneath the surface of the Mediterranean Sea grows one of the oldest and largest living organisms on Earth — and most people have never heard of it. Neptune Grass spreads through underground rhizomes, forming vast meadows on the seafloor. A single clone discovered off the coast of the Balearic Islands is estimated to be between 80,000 and 200,000 years old. It also produces the oxygen for roughly half of the Mediterranean Sea's marine life!