This article reconstructs the voyage of the Swimming Lion to the Caribbean in 1595 and the court battle to which it gave rise. The Master mariner Gillis Dorenhoven was accused of piracy by Pedro d'Arana, contador of Havana, who sued his employers before the Middelburg Admiralty Court in 1609–1610. Johan Boreel, the eldest son of one of the defendants, sought expert advice from his friend Hugo Grotius. The author of Mare Liberum, published in April 1609, became involved in the case at various levels. Pressure was put on the States General to revise their instructions for the Admiralty Court. Grotius also tried to convince the Admiralty judges that freedom of trade and navigation was a fundamental right of Dutch merchants in the West Indies and that Dorenhoven's actions should be seen in this light. For political reasons, he could not refer to the Americas in Mare Liberum. Yet the case of the Swimming Lion reveals just how expansive his notion of freedom of trade and navigation really was.