Floating booms constitute a fundamental too] for the protection of marine and coastal ecosystems against accidental oil spills. Their containment performances in exposed areas are often impaired by the action of waves, currents and winds in a manner which is dependent on the boom's response as a floating body, and which is not fully understood at present. In this work the relationship between the design parameters of a floating boom section and its efficiency against the mode of failure by drainage under a variety of wave and current combinations is investigated by means of physical modelling. Seven boom models with different geometries and buoyancy-weight ratios are tested with an experimental setup that allows them to heave and rotate freely. The model displacements under waves (both regular and irregular) and currents, as well as those of the free surface adjacent to the model, are measured with a Computer Vision system developed ad hoc. Two efficiency parameters are defined-the significant and minimum effective boom drafts-and applied to the results of an experimental campaign involving 315 laboratory tests. Thus, the manner in which the design parameters influence the boom's efficiency under different wave and current conditions is established. (C) 2009 Elsevier B.V. All rights reserved.