From 1768 to 1779, Captain James Cook led three voyages on behalf of the British Admiralty in the hope of finding a Northwest Passage. While ultimately unsuccessful, published accounts of these voyages chronicled the exploration of other uncharted geographies, serving as an introduction for eighteenth-century readers to wider Atlantic and Pacific worlds. Functioning in part as military reports, these accounts made visible systems of exchange between European states and Atlantic and Pacific peoples by carefully detailing goods moving on and off the ships and formal relationships on shore. This chapter argues that in privileging formal systems of control and exchange, Cook’s accounts obscures the many informal (and often illicit) methods of economic and cultural exchange enacted between sailors and indigenous peoples. Looking specifically at the practice of taking local women on board ships and allowing willing sailors to trade goods for sex, it demonstrates that by using the language of contagion to describe these relationships between sailors and native women—rather than the language of capitalist exchange employed elsewhere to describe relationships between British naval officers and native men—Cook’s accounts mask systems of illicit trade in which women’s bodies are commodified as objects of material exchange.