This dissertation explores the technoscientific construction of the Yucatec Karst Aquifer Systemas a site of political contestation. Framed by the global concerns about aquifer depletion and contamination and the local concerns about growing industrialism and touristification in the region, this academic work provides a rigorous ethnographic account of how aquifers become matters of concern for various publics and essential sites for collective mobilization and political resignification. Based on eighteen months of ethnographic fieldwork in the Yucatán Peninsula, This dissertation examines the practices of cartographers, speleologists, chemists, geomorphologists, and lawyers in their collective effort to reconfigure sovereignty, territoriality, and Indigeneity through their representation of the subterranean. By analyzing the rich social life of the largest aquifer in Mexico, this dissertation examines how different forms of territorial sovereignty emerge from the technical arrangements of thousands of sinkholes, geological fractures, large cave systems, and groundwater reservoirs that make territorial, social, and political difference legible to the Mexican State. In a national context where the government has embarked on an ambitious national reform, large-scale infrastructure, and widespread agro-industrial growth are transforming the Mexican landscape in previously unseen ways. Amid all of this, this dissertation shows how the aquifer as an environmental object has become central in constituting and controlling the borders, boundaries, and bodies of the Mexican State.