There are mountains on land and there are mountains under the sea. The vast ocean seems flat but under that water are mountains, valleys and plains. These mountain chains rival the Alps, the Andes and the Himalayas in size and little is known about seamounts, the vast mountains hidden under the world’s oceans. Now in a special issue of Marine Ecology scientists uncover the mystery of life on these submerged mountain ranges and reveal why these under studied ecosystems are under threat.