A rip current is a phenomenon that occurs along shorelines with breaking waves. As the wave moves from deep water to shallow water it may break with a great deal of force in some places, while it is weak in other areas. This difference in strength of the wave's break can cause circulation cells to develop which form the rip current: a narrow and fast-moving strip of water that moves away from the shore. A variety of factors may affect the formation of the current including sandbars, piers, jetties, and the shape of the ocean floor.
Rip currents are often erroneously referred to as rip tides. Tides have to do with the ocean's water levels which predictably and slowly change primarily due to the moon's gravitational pull. Rip currents, on the other hand, exist irrespective of tides, forming suddenly and unexpectedly as a result of certain conditions of breaking waves. Put simply, tides have to do with the water level, and currents are faster streams of water moving in a larger body of water.
A rip current is also different than an undertow which is a current of water pulling down to the ocean floor. An undertow therefore will pull a swimmer down, while a rip current will typically pull a swimmer out into the ocean.
This condition can be serious when it forms at a public beach, particularly for those who cannot swim well or at all. This is because current speeds are usually around one to two feet per second (about .3 to .6 meters per second). In some cases, a rip current may travel at speeds faster than eight feet per second (about 2.4 meters per second) – faster than an Olympic swimmer can swim. Therefore even the best of swimmers can be in danger if they do not know how to react if they find themselves in this current. Due to its speed and force, these currents result in more than 100 drowning deaths every year in the United States and have some relation to approximately 80% of water rescues.
To avoid drowning in a rip current, it is important to recognize sea conditions. Areas in the water that are a different color than surrounding water can be a sign of a rip current. Choppy, churning water is another sign, as is a line of seaweed, foam, or other debris moving forward in the water.
Conversely, unusually calm looking waters can also be a sign. A break in the pattern of the waves moving toward the shore may also mean a rip current is brewing beneath the water’s surface. It should be noted, however, that the current may be present and not exhibit any of these signs.
To remain safe, swimmers should never swim alone and should exercise extreme caution when swimming at beaches without lifeguards on duty. Swimmers caught in a rip current should remain calm and swim in a direction that follows the shoreline, swimming to shore only once they are out of the current. If swimming along the shore is not possible, one should float or tread the water until free of the current. Attempting to swim toward shore while caught in the current will only result in exhaustion.