The water moving up a beach from a breaking wave. The swash zone involves a moving land–water boundary travelling across the beach; at least some part of the beachface is usually unsaturated. Water depths in the swash zone are very shallow, and sediment is often transported as complicated, single-phase, granular-fluid flows (Horn (2002) Geomorph. 48, 1–2). Swash-aligned beaches are parallel to the incoming wave crests and net longshore drift is at a minimum.