All along the Pacific Coast of North America, giant stands of kelp up to 100 feet high, like this one in California"s Channel Islands, provide habitat for a vast number of fish, invertebrates, and sea mammals. Giant kelp, technically a type of brown algae, is the largest of all seaweed and one of the fastest-growing of any organism—as much as 2 feet per day! The gas-filled pods you see in this image help the kelp float. Like the trees in the Amazon, the kelp forests of our oceans are key to the health of marine life.