The paper offers an alternative interdisciplinary approach to dealing with lhe complexity associated with groundwater resources, providing a new angle thai inlegrates deep grotindwater systems as defined by hydrogeologists with a paradigm shift In natural resource governance, developed by political scientists. It questions the piecemeal approach to governance of groundwater resources, coupled with the lack of acknowledgment regarding the hydraulic connection ol vast deep aquifers-or a hidden sea of groundwater. Rather than relying on ttaditional approaches to groundwaler governance, which treat the resource like a mineral resource underlying lhe houndaries of a sovereign nation, the "post-sovereignty" and "multi-level" governance model proposed here for groundwater resources acknowledges that groundwater is hydraulically connected to the ocean and is equally complex with respect to predictive modeling. Existing legal instruments as.sociated with the ocean that fall under the global "contract" of the UNCLOS. together with ongoing efforts to develop a legal instrument for transhoundary aquifers, offer useful lessons. The paper concludes thai a "world water contract" or Law of the Hidden Sea could be adapted to incorporate groundwater as a global common, deep aquifers thai are not in direct hydraulic connection with surface water resources and that are part of the developing common heritage of mankind.