This Article traces the Admiralty action in rem back to its civilian roots in medieval Europe and shows how the action in England gradually diverged from the Continental model, beginning in the sixteenth century. The action in rem and the arrest of ships in the contemporary law of the United Kingdom, the United States, and Canada are outlined and compared to the civilian saisie conservatoire and its counterpart, the U.S. maritime attachment. Two relatively new procedures employed in modern maritime law in the U.K. and British Commonwealth countries--the Mareva injunction and the Anton Piller order--are also discussed. The author concludes with some incisive comments on salient points in the Arrest of Ships Convention 1999 and the urgent need for greater international uniformity in this vitally important area of maritime law.