Drawing on ethnographic research in the Falkland Islands (Malvinas), this paper analyzes how disputed oil interests become embedded in data infrastructures for environmental governance. Nearly four decades after a war that cemented the South Atlantic archipelago’s British status, offshore oil discoveries have led Argentina's government to renew its sovereignty claim, arguing that the islands are within its waters. Nonetheless, the British Falkland Islands Government (FIG) has licensed unilateral drilling. Centering on a “data gap” project, financed by the FIG and its oil licensees, the article describes how marine ecologists tag penguins with tracking sensors, as part of a new geographic data infrastructure for the South Atlantic. Data representing penguin foraging are supposed to feed into environmental impact assessments for oil exploration. The article demonstrates how these data and confidence ratings in environmental impact statements reinforce access to and control over maritime territory and resources. Extending recent claims that data have become key actors within environmental governance networks, this research finds that particular data practices may actually enhance fossil fuel industry interests through measures of transparency, leaving ambiguous matters related to transboundary impacts and local pollution unresolved.