Seagrass meadows are the most powerful natural CO₂ sinks, surpassing forests. They support biodiversity, stabilize sediment, clear water and protect coasts, yet remain unexplored and are threatened by human activities and climate change. Natural recovery cannot offset this loss. I developed a citizen-science research kit based on PROJECT MANAIA’s protocol that enables standardized monitoring and mapping of seagrass meadows through simple tools, clear guidelines and a dedicated app with open data sharing to generate large-scale comparable data while raising awareness and scientific literacy.