The capacity for individuals to move long distances can profoundly influence how species are affected by localised threatening processes. Previous studies on the movement patterns of sea snakes have highlighted the highly site-attached nature of some species, but constraints on collecting data at large spatial and temporal scales have underestimated the snakes' capacities for dispersal. Here we used acoustic tags implanted in four species of free-ranging sea snakes to provide the first records of long-distance movements by these large marine predators. Although most movements recorded were within 2 km of the snake's release site, some individuals moved farther than has previously been recorded for any sea snakes. We recorded displacements from capture-release sites of up to 13 km in Hydrophis coggeri and 15 km for Hydrophis major. Thus, although some sea snakes are highly philopatric to small areas, others travel over larger areas and hence may be less vulnerable to localised threats.