Seagrass: green leaves swaying in the currents. Fish weave their way through, and sea turtles graze. They're always on their guard, watching out for any encroaching sharks. The seagrass' roots are hidden in the seabed, where they anchor the sand, securing the coastline. The best-kept secret is the amount of carbon these plants store: even more than trees do. But seagrasses are facing a barrage of threats. We urgently need to protect them, and enable the rewilding of the sea.