They attack beachgoers, aquafarms, power plants, and even aircraft carriers: jellyfish are a growing problem in coastal areas across the planet. The jellyfish threat is, however, at least partly produced by humans themselves. Climate change, overfishing, plastic waste production, ocean acidification and other man-made environmental problems threaten the health of the ocean and make jellyfish thrive. In his latest article, “Jellyfish Encounters: Science, Technology and Security in the Anthropocene Ocean” IFSH-researcher Delf Rothe studies how scientists, enterprises, and international relations have reacted to this emerging threat. With their complexity jellyfish blooms are almost entirely unpredictable and thus overcharge existing regimes of risk management and security. As a result, countermeasures against jellyfish attacks increasingly rely on digital technologies: from drone-based early-warning to autonomous killer robots with object detection capabilities. Rothe uses these and further examples to discuss the changing relation between knowledge, technology and security in an age of increasing environmental risk.