Where waves arrive in rapid succession, a rip may occur, allowing the piled-up water to flow back to the sea. Because rips are narrowly focused currents, swimmers should swim out of them in a direction parallel to the beach. Where rips occur, the water level is lowest and so are the waves. Where water flows towards the beach, both the water level and the waves are highest. A swimmer should swim to such a place.
Some beaches have irregularities such as under water reefs where rips always form.
Don't swim near reefs and groynes. This diagram provides an aerial view of rips and cusps. The left side shows waves heading straight for the shore. If the shore is exactly the same everywhere, a rip may form anywhere. It causes a current jet back to sea and two corresponding deep eddies.