Understanding the forces beneath the ocean surface is paramount for beach safety. Many beachgoers struggle to identify or confuse the different types of strong coastal currents. Knowing how to visually spot a dangerous current from the shore provides the moments needed to choose a safe swimming location. Recognizing these indicators and having a clear plan for what to do if caught are essential for a safe experience near the water.
Clarifying the Terminology
The term “undertow” is frequently used to describe any strong current that pulls a swimmer, but it refers to a different, less dangerous phenomenon than the one responsible for most rescues. A rip current is a powerful, narrow channel of water flowing away from the shore, extending through the line of breaking waves. This seaward-moving water is the primary hazard, reaching speeds up to eight feet per second.
Rip currents are responsible for over 80% of rescues performed by surf beach lifeguards in the United States, making them the most significant threat to swimmers. In contrast, the true “undertow” is the general subsurface backflow that occurs immediately after a wave breaks. This backwash is localized, temporary, and pulls objects or people down and back toward the sea floor, rather than carrying them far offshore.
Visual Indicators of Rip Currents
The most deceptive sign of a rip current is often an area of water that appears unusually calm compared to the turbulent, breaking waves around it. This apparent stillness is a gap in the incoming wave pattern because the strong, opposing current suppresses the incoming surf. Swimmers are often lured into these calm areas, mistaking the lack of breaking waves for safety.
Another clear indicator is a channel of water that looks distinctly choppy, turbulent, or churning. This rough texture is caused by the powerful, rapid flow of water moving offshore, often against the incoming swell. This narrow, agitated channel will appear different from the smoother water on either side where waves are consistently breaking.
The current’s force scours the seabed, stirring up sand and sediment, which makes the water appear discolored or murky. This plume of sediment may look brownish or darker than the surrounding clear water and extends perpendicularly away from the beach. A line of foam, seaweed, or debris consistently moving seaward is a definitive sign, as the rip current carries floating material out past the breaker zone.
Locating Strong Backwash
The phenomenon commonly mistaken for a dangerous undertow is actually a strong backwash, which is the water rushing back down the beach slope after a wave has washed up. The intensity of this backwash is directly related to the beach’s profile and sediment composition. Steeper beaches create a much faster and more powerful backwash because gravity acts more strongly on the returning water.
This force is primarily felt in the shallow swash zone, the area where waves run up and recede, and it can destabilize a person’s footing. While a strong backwash can be startling and may briefly knock a person down, it is a temporary effect of the wave cycle. It does not pose the same threat of carrying a person far out to sea like a rip current does.
Beaches with finer sand particles and a gentler slope tend to have a weaker backwash because the water has more time to percolate into the sand. Conversely, coarse-grained beaches or those with a steep drop-off near the shore produce a more immediate and forceful backwash. Understanding that this strong, temporary pull is different from the continuous, offshore pull of a rip current is an important safety distinction.
What to Do If Trapped
If you find yourself caught in a strong seaward pull, the first step is to remain calm and conserve energy. Do not attempt to swim directly back to shore against the current, as this will quickly lead to exhaustion. A rip current is a narrow channel, and fighting it head-on is ineffective.
Instead, swim parallel to the shoreline, across the current’s flow, until you feel the pull weaken. Rip currents typically dissipate just beyond the breaking wave line, so swimming sideways allows you to exit the fast-moving channel. Once out of the current, swim at an angle back toward the beach. If you are too tired to swim, simply float or tread water and wave your arms to signal for help.