Monstrous tsunami waves, like the one that killed over 200,000 people in the Indian Ocean in 2004, create an electric field as they form. This field could possibly be sensed by a network of underwater sensors. Such a network would be extremely valuable but also prohibitively expensive to build. Researchers at the National Oceanic and Atmospheric Administration (NOAA) propose, however, that the existing large network of undersea communication cables could be used instead. That finding could lead to early warnings that may complement existing tsunami warning systems.