The invention concerns one or more floating barriers for use together with a conventional floating barrier for use in collecting oil on a water surface. The floating barriers are of the kind where the submerged part is partially penetrable for water and oil, thereby providing an impeding but not blocking effect on a passing flow of water. The function of the floating barriers is based on the fact that by disposition upstream relative to the conventional floating barrier and together with the latter they will constitute a total system which can be moved through an oil-contaminated body of water with substantially greater speed than a conventional floating barrier, without leaking oil behind the floating barrier system. The invention particularly concerns conditions of the geometry, spacing and draught of the water-penetrable liquid barriers.