Marine extraction accounts for one third of the world's hydrocarbon production. Several analyses suggest that seismic surveys employed in oil exploration harm marine life; however, their long-term impacts have not been extensively studied. We examine debates between fishers, the oil industry, and governmental authorities over the effects of oil explorations in Tabasco, Mexico. The study employs ideas from historical ontology in tracing the contested production of truth-claims about exploration in the context of scientific uncertainty. It shows how actors, through their different engagements with the sea, and with different degrees of power, frame claims about the relations between exploration and fish. We argue that fishers, through their efforts to "think like fish" produce situated knowledges about the effects of oil exploration. They explain a disappearance of fish by their understanding that seismic surveys disturb fish migration, impair the hearing of fish and cause fish death. Oil company and governmental representatives frame the impacts of oil exploration as insignificant by separating environmental and social dimensions, by isolating individual exploration events, and by arguing that possible effects are transitional. Due to scientific indeterminacy, oil exploration is malleable in the hands of powerful political representations that understate its possible impacts on marine socio-environments.