Rips & Undertows

We surfer's call them "rip currents" and many lifeguards call them "run-out", but by any name they can be terrifying to the uninitiated or weak swimmer/surfer. They consist of a rapidly flowing current running from the near beach area, inside the breaking waves, out to sea. In most cases they flow faster than a person can swim, even with swim fins on, and they carry one out well beyond the surf. But this is only part of the problem!

Imagine that you are playing in 3 to 5 foot breakers, diving through them and body surfing back to the beach, generally unconcerned because you are only a few feet from the warm sand. Suddenly your feet don't touch bottom any more and you notice you are farther from the beach. "No sweat." You turn and swim for the beach, only a few feet away, where the sunbathers are so close you can watch them applying suntan lotion to each other. A quiet, almost pastoral scene. But they are getting further away! You put on a burst of speed but they still get further away. Now panic, the great killer, appears. You are scared and put everything you've got into one last spurt for the beach. You are, typically, out of shape and soon, gasping, take in a mouthful of salt water and sink. The rip current has claimed another victim. Because you reduced your buoyancy by inhaling a lot of seawater, replacing air in your lungs, your body sinks. It was not the undertow pulling you under, it was the inhaled water, making your body negatively buoyant, that took you under. Either way it was fatal!

Another factor helps with the panic. Safety is only a few yards away and one is sure that another short spurt will get you to the beach where kids are playing in the sand and lovers are necking in the sun! That final desperate spurt often does the swimmer in.
The terrible thing is, it was so unnecessary. A very simple rule will save your life if you are ever in this position. SWIM PARALLEL TO THE BEACH. Refer to the drawing to see how and why this helps. The rip is a narrow stream and, once out of it, you can turn toward the beach in perfect safety. It has saved many lives and could save yours. Remember this rule. And now the reasons for rips.

There are two main cases for rips on open coasts. One is for a coast or beach with no underwater obstructions. The scheme works like this: As waves cross the ocean in deep water (defined as being deeper than half of the distance between two wave crests) the water under the wave moves in circular orbits, with very little forward motion of the water. Only the wave shape advances.
When this wave gets into water shallower than half the distance between the crests, it begins to drag the bottom and changes occur in the wave characteristic. It shortens as the forward crest slows down and the following crest catches up. As it shortens it gets higher, exactly what the surfer looks for on a surfing beach.
Instead of orbital water motion the wave breaks and the water now moves forward and up onto the beach. Each succeeding wave brings more water onto the beach and only a portion of it goes back. The result is a buildup of water; a pile of water getting more unstable with each succeeding wave. It is held on the beach by the breakers. Finally a part of one breaker is a bit lower than the rest and the "wall" of water piled up inside breaks through and flows out to sea as a rip. This lowers the pile in this spot and the pileup both up and downbeach from the spot flows into the low spot and out to sea. These currents feed the rip and so are called feeder currents. In extreme cases they are strong enough to knock children down and roll them into the rip current. As long as the waves bring water to the beach about as fast as it flows out to sea, the rip continues. When the waves die down, the rip ceases.

The second case results in an even more pronounced rip. It occurs when a sand bar (or nearshore reef) acts as a barrier, over which waves break. The barrier holds the water on the beach and it finds its way back out to sea through a gap in the bar or reef. Obviously this should be a strong rip and in the case of the reef, usually a permanent rip. In California we used them to transport SCUBA divers out beyond the surf, but we came back in almost anywhere else but in the rip.

I've tried to swim against a rip with swim fins and found myself going feet first out to sea. Just don't panic - swim parallel to the beach. You can often tell a rip because the water flowing out to sea beats down the incoming waves and a surface track of white foam often indicates its position. Sometimes the sand being carried out makes the rip muddier than the water around it. Watch for these tell tale signs and pay attention to the lifeguards. They are very savvy about runouts and post RIP CURRENT warnings on their bulletin boards. Learn the simple rule and save your life or one of your friend's.