As
ocean surface waves come closer to
shore they
break, forming the foamy, bubbly surface called . The region of breaking waves defines the
surf zone. After breaking in the surf zone, the waves (now reduced in height) continue to move in, and they run up onto the sloping front of the
beach, forming an uprush of water called
swash. The water then runs back again as backswash. The nearshore zone where wave water comes onto the beach is the surf zone. The water in the surf zone, or breaker zone, is shallow, usually between 5 and 10 m (16 and 33 ft) deep; this causes the
waves to be unstable.