As we watch continuous news coverage of heat waves, wildfires, epic floods and beaches full of dead fish due to unprecedented ocean temperatures, action is being taken at the international level to clarify state obligations under the law of the sea convention as they pertain specifically to climate change. In the face of the stubborn remaining large gap between what is necessary and what is actually being done to mitigate the worst of climate change, systemic climate litigation in national courts is gaining in importance as a driver of more ambitious climate action. This paper considers the implications of a hypothetical inclusion of law of the sea due diligence arguments in national systemic climate litigation as a potential tool to require states to significantly increase their immediate- and near-term ambition to dramatically reduce GHG emissions.