The project OceanNETs aims to determine to what extent, and under what conditions, the large-scale deployment of ocean-based negative emission technologies could contribute to achieve climate neutrality. Humanity cannot limit global warming to 1.5 °C unless much more action is taken. In addition to reducing emissions to nearly zero, humanity must also actively remove CO₂ from the atmosphere. The OceanNETs project brings together the expertise needed to answer major open questions concerning ocean-based Negative Emission Technologies for climate stabilization.