This brown algae and its cousins love coastal waters that are cool or cold. Some form wispy clusters of filaments, while others resemble delicate ribbons or leafy, golden-brown shrubs. One of its relatives forms the kelp forests that thrive off the California coast. It can grow as much as a foot a day, producing what are considered the largest of the sea's photosynthetic organisms.
Photo: Sylvia Earle/National Geographic
Mapping the Sea and Its Mysteries