Seagrasses provide the foundation of highly productive ecosystems present along the coasts of all continents except Antarctica, where they rival tropical rain forests and coral reefs in ecosystem services. In colonizing sedimentary shorelines of the world’s oceans, seagrasses found a vast new habitat free of terrestrial competitors and insect pests, but had to adapt to cope with new structural and physiological challenges related to full marine conditions. An international research team has completed the first comprehensive genome analysis of Zostera marina, the most widespread seagrass species throughout the temperate northern hemisphere.