A cyclonic separator with an inlet, a fuel outlet, an inner wall comprising a water-permeable material, an outer wall, a cavity between the inner wall and the outer wall, and a water outlet. The cyclonic separator is adapted to discharge water from the water outlet via the cavity and relatively less dense liquid fuel from the fuel outlet. The water-permeable material enables water in the cyclonic separator to flow through the water-permeable material into the cavity, but substantially prevents liquid fuel in the cyclonic separator from doing so.