They come in some 13,000 known species, from glimmering-blue sea sapphires to noodle-shaped cod worms. Some roam freely, while others cling to plants or animals. One copepod species can swim into ...

Satellite data, in other words, only gives a rough idea of what lies beneath the sea. Only a tiny percentage of the ocean floor has been carefully mapped, which means we know less about 71 percent ...