With climate change and the resultant sea-level rise projected already for this century, fundamental challenges for international law may be on the horizon. Core aspects of international law rely on the general stability of geographical conditions. Coastal geography, due to its perceived stability, serves as the key objective circumstance on the basis of which the rights of states to maritime zones are determined, and maritime delimitation disputes resolved. A defined territory is a constituent element of statehood under international law. In the not-too-distant future, important questions may arise about the sustainability of those aspects of international law, while other aspects, such as the population of the state - and, accordingly, human rights - may gain in prominence and acquire new dimensions, all likely to require profound re-examination of currently accepted paradigms of international law. This article briefly addresses three questions: first, are the prospects of sea-level rise already a real concern from the viewpoint of international law? Second, what is the relevance of this perspective for current international law? And third, how should international law in the future approach the phenomenon of sea-level rise?