Soap or oil leave fleeting traces on the water surface, the movement of human beings is only visible in the moment—the traces of fishermen, military, and pirates are liquid and get lost in the sea. A problem for the reconstruction of events after shipwrecks or accidents. What happened and how? With a view of the Mediterranean and the controversial EU border policy, who was where or broke which law, failed to assist? How do the states respond to this, and what strategies do they use to control movement with laws, location devices, and visible controls, but also by obliterating visible traces, and who controls this so-called regime of movement? In case studies of forensic architecture, techniques are presented that solidify the fluid into legible traces and tangible arguments.