Tsunamis are infrequent but terrifying hazards for coastal communities. Difficult to predict, they materialise with little warning, claiming thousands of lives and causing billions of dollars in damage. Recent mega-tsunamis in Japan and Indonesia claimed close to 250,000 lives, triggering wide-scale economic and social disruption. Developing countries cannot afford costly underwater cable systems, and governments and relief organisations have been forced to rely on flawed warning systems such as deep-sea buoys. Now, a ground-breaking new approach to tsunami detection and warning, which relies...