A rip current, commonly referred to simply as a rip, or by the misnomer “rip tide“, is one specific kind of water current that can be found near beaches. It is a strong, localized, and rather narrow current of water. It is strongest near the surface of the water, and it moves directly away from the shore, cutting through the lines of breaking waves.
Rip currents can occur at any beach where there are breaking waves: on oceans, seas, and large lakes. The location of rip currents can be unpredictable: while some tend to recur always in the same place, others can appear and disappear suddenly at various locations near the beach.
A rip current is one of the most dangerous natural phenomena you can encounter in the sea. These currents kill both regular and professional swimmers. This is often the result of a person simply not knowing what they should do when they encounter them.
You can try to resist the current, but it won’t work. And then when you realise that this is the case, panic sets in — and that’s not going to help you either.
Rip currents are especially dangerous if they occur in shallow waters where there is a gently sloping, low-lying coastline surrounded by tongues of sand, shoals or islets (the Gulf of Mexico or the Sea of Azov, for example). In such cases, the mass of water is unable to return to the open sea at low tide because of these natural barriers. The pressure placed on the point where the flow of water joins with the sea grows significantly. Rapids form, with the water rushing back towards the sea at around 2.5-3 metres per second and forming a kind of river in the middle of it.
This is what it looks like. The diagram below shows the reverse flow of water moving at a right angle to the shore, in the direction of the sea:
These corridors of water can appear at any point along the beach. Waves roll along one after another, bringing more and more water and returning out to sea at varying speeds, thereby forming a reverse flow — that is, the river-like phenomenon noted above:
In the following photo you can clearly see the reverse flow of the water, as well as some unfortunate people who have become caught up in it:
Usually, rip currents are narrow — just 2-3 metres, and they move at a speed of around 4-5 kilometres an hour. These ones aren’t particularly dangerous. However, they can be as much as 50 metres in width and 200-400 metres in length, and achieve a speed of 15 kilometres an hour.
How can you detect these currents and avoid getting trapped in them? Look out for thefollowing signs:
- A channel of fast-flowing water moving at a right angle to the shore.
- The water in the area around the beach or coastline is a different colour (there will be a white area surrounded by green or light blue).
- An area made up of foam, marine vegetation and bubbles flowing steadily in the direction of the open sea.
- A 5-10 metre gap in an otherwise compact area of inward-flowing waves.
If you see any of the things described above, you’re lucky, because it means that you’ve detected the rip current before you’ve had a chance to get caught up in it. Don’t go and swim there. But what if you didn’t see any of these four signs? Bad news, because 80% of dangerous rip currents cannot be identified by sight.
Remember, rip currents can occur anywhere along the shore. If you stand in the water only up to your waist, and definitiely if you’re in it up to your chest, a rip current can seize you and carry you out to sea. Of course, people who don’t know how to swim often do exactly this — they enjoy themselves by simply staying in one place. So under no circumstances should you go into the sea far from other people, and of course, always pay attention to the red flags and any warning signs placed on the beach.
What to do if you get caught in a rip current
- Don’t panic!
When we’re in a state of panic, our actions are determined by our instinct for self-preservation, and it becomes a lot harder to take rational decisions. If you actually know what you need to do when you get caught in a rip current, you have every chance of surviving.
- Save your strength!
Don’t struggle against the flow of water by trying to swim directly back to the shore. Unfortunately, this won’t achieve anything other than to use up all your energy. Instead of swimming towards the shore, swim parallel to it. If the rip current is narrow (up to 5 metres), you’ll be able to escape it very quickly.
- If the rip current is wide (20 metres or more), what should I do?
It won’t be easy to escape in this case, even if you follow the rules and swim parallel to the shore. But again, when you realise that you can’t get out, don’t panic! Just relax, because the reverse flow of water won’t last for very long; it will stop within about 5 minutes. Once it’s stopped, first swim about 50-100 metres parallel to the shore, and then towards it. If you try to go straight towards it, there’s always the chance that the flow will start again in the exact same place, and you’ll be stuck again.
Important things to remember
- A rip current will never drag you under
Rip currents are not the same thing as whirlpools. They drag you along the surface of the water, and never down to the sea bed.
- The width of a rip current is always limited
Usually they are never more than 50 metres in width. More often than not, they don’t exceed 10-20 metres. Once you’ve swam just 20-30 metres along the shore, then you should be able to feel that you’re safely out of it.
- The length of a rip current is always limited
The flow of water always weakens relatively quickly, coming to an end at the point where the waves reach their peak and begin to crash down. Surfers call this area the ’line up’; usually it’s no further than 100 metres from the shorelin
Rip currents are powerful, narrow channels of fast-moving water that are prevalent along the East, Gulf, and West coasts of the U.S., as well as along the shores of the Great Lakes.
Moving at speeds of up to eight feet per second, rip currents can move faster than an Olympic swimmer.
Panicked swimmers often try to counter a rip current by swimming straight back to shore—putting themselves at risk of drowning because of fatigue.
Lifeguards rescue tens of thousands of people from rip currents in the U.S. every year, but it is estimated that 100 people are killed by rip currents annually. If caught in a rip current, don’t fight it! Swim parallel to the shore and swim back to land at an angle.
While the terms are ofter confused, rip currents are different than rip tides. A rip tide is a specific type of current associated with the swift movement of tidal water through inlets and the mouths of estuaries, embayments, and harbors.
A rip current forms because breaking waves push water towards the land. Water that has been pushed up near the beach flows together (as feeder currents), and this water finds a place where it can flow back out to sea. The water then flows out at a right angle to the beach in a tight current called the “neck” of the rip, where the flow is most rapid. When the water in the rip current reaches outside of the lines of breaking waves, the flow loses power, and dissipates in what is known as the “head” of the rip. Sometimes tendrils of left-over current then actually curve back towards the shore.
Rip currents can be hazardous to people who are in the water. Swimmers or floaters who are caught in a rip and who do not understand what is going on, may not have the necessary water skills, may panic, or may exhaust themselves by trying to swim directly against the flow of water. Because of these factors, rips are the leading cause of rescues by lifeguards at beaches, and in the US rips are responsible for an average of 46 deaths from drowning each year.
A rip current is not the same thing as undertow, although some people use the latter term when they mean a rip current. Contrary to popular belief, neither rip nor undertow can pull a person vertically down and hold them under the water surface; A rip simply carries floating objects, including people, to an area outside the zone of the breaking waves.
When wind and waves push water toward the shore, that water is often forced sideways by the oncoming waves. This water streams along the shoreline until it finds a suitable exit route back out to the open water, straight out, at a right angle to the beach. This return flow of water is called a rip current. Rip currents are usually quite narrow, and are located in places such as where there is a gap in a sandbar, under piers, and along jetties.
A fairly common misconception is that rip currents are somehow able to pull a swimmer vertically down, under the surface of the water. This is not true, and in reality a rip current is strongest close to the surface. This strong surface flow tends to damp the effect of incoming waves, leading to the illusion of a calm part of the sea, without waves, which may possibly attract some swimmers to that area. The offshore path taken by a rip current can be demonstrated by placing colored dye at the start of a current at the shoreline.
A more detailed description involves a quantity known as radiation stress. This is the force (or momentum flux) exerted on the water column by the presence of the wave. As a wave shoals and increases in wave height prior to breaking, radiation stress increases. To balance this, the mean surface (the water level with the wave averaged out) decreases—this is known as setdown. As the wave breaks and continues to reduce in height, the radiation stress decreases. To balance this force, the mean surface increases—this is known assetup. As a wave propagates over a sandbar with a gap (as shown in the lead image), the wave breaks on the bar, leading to setup. However, the part of the wave that propagates over the gap does not break, and thus setdown will continue. Thus, the mean surface over the bars is higher than that over the gap, and a strong flow issues outward through the gap.
Rip currents can potentially occur wherever strong longshore variability in wave breaking exists. This variability may be caused by such features as sandbars (as shown in the animated diagram above), by piers and jetties, and even by crossing wave trains. Rips tend to be more common, wider and faster, wherever (and whenever) breaking waves are large and powerful. Varying underwater topographymakes some beaches more likely to have rip currents; a few beaches are notorious in this respect.
Although rip tide is a misnomer, in areas of significant tidal range the rip currents may only occur at certain points of the tide. Too much water over the bar will not cause waves to break over the bar as, of course, will too little. If the shoreline shelves gently, the area behind the bar may vary from a few feet to a mile or more in the course of an hour or two.
Danger to swimmers
Rip currents are a potential source of danger for people who are in shallow water with breaking waves in seas, oceans and lakes. Rip currents are the cause of 80% of the rescues carried out by beachlifeguards.
Rip currents typically flow at 0.5 metres per second (1–2 feet per second), but they can be as fast as 2.5 metres per second (8 feet per second), which is faster than any human can swim. However, most rip currents are fairly narrow, and even the widest rip currents are not very wide; swimmers can easily exit the rip by swimming just a few strokes at a right angle to the flow, parallel to the beach. Swimmers who are unaware of this fact may exhaust themselves trying unsuccessfully to swim against the flow. The pull of the current also fades out completely at the head of the rip, outside the zone of the breaking waves, so there is a definite limit to how far the swimmer will be taken out to sea by the flow of a rip current.
In a rip current, death by drowning occurs when a person has limited water skills, or panics, or persists in trying to swim to shore against a strong rip current, thus eventually becoming exhausted.
According to NOAA, over a 10-year average, rip currents cause 46 deaths annually in the United States, and 64 people died in rip currents in 2013. However, the The United States Lifesaving Association“estimates that the annual number of deaths due to rip currents on our nation’s beaches exceeds 100.”
A study published in 2013 in Australia revealed that rips killed more people on Australian territory than bushfires, floods, cyclones and shark attacks combined.
Recognizing and identifying rips
Rip currents have a characteristic appearance, and this means that with practice, and using careful observation, lifeguards, beachgoers, and water users can learn to notice and identify rips, thus generally being able to avoid them. Rip currents often look almost like a road or a river running out to sea, away from the shore. Rip currents are easiest to notice and identify when the zone of breaking waves is viewed from a high vantage point. Beachgoers can also talk to lifeguards, who are always watching for rip currents, and who will move their safety flags so that swimmers can avoid rips. The following are some characteristics that a person can use to visually identify a rip before entering the water:
- There is a noticeable break in the pattern of the waves: the water often looks flat where the rip is, in contrast to the lines of breaking waves on either side of the rip.
- A “river” of foam: the surface of the rip sometimes looks foamy, because the water is churned up.
- Different color: the rip usually differs in color from the surrounding water; it is often more opaque, cloudier, or muddier, and so, depending on the angle of the sun, the rip may show as darker or lighter than the surrounding water.
- It is sometimes possible to see that foam or floating debris on the surface of the rip is moving out, away from the shore. In contrast, in the areas of breaking waves, floating objects are being pushed towards the shore.
These characteristics are helpful in learning to recognize and understand the nature of rip currents so that a person can recognize the presence of rips before entering the water. In the US, some beaches have signs created by NOAA and USLA, explaining what a rip current is and how to escape one. These signs are entitled, “Rip Currents; Break the Grip of the Rip”.
Dealing with a rip
A swimmer or floater who is caught in a rip current may notice that he or she is moving away from the shore quite rapidly. It is often not possible to swim directly back to shore against a rip current, so this is not recommended. However, contrary to some popular misunderstandings, a rip is not capable of pulling a swimmer under the water; instead it simply carries the swimmer away from the shore in a narrow channel of water. The rip is like a treadmill, which the swimmer needs to step off. One effective response is to remain calm and swim parallel to the shore until the swimmer exits the rip current, which is usually not very wide. Once out of the rip, swimming back to shore is fairly easy in areas where waves are breaking and where floating objects (including swimmers) are being pushed towards the shore.
As an alternative, swimmers or floaters who are caught in a strong rip can instead relax and calmly float on their back or tread water. Eventually the rip current will lose its momentum, and the swimmer is then able to signal for help by raising one arm, or to swim at a leisurely pace, in a diagonal direction, away from the rip and back to shore.
It is necessary for coastal swimmers to understand the danger of rip currents, to learn how to recognize them and how to deal with them, and if possible to swim in only those areas where lifeguards are on duty.
Experienced and knowledgeable water people, including some surfers, body boarders and kayakers, will sometimes use rip currents as a rapid and effortless means of transportation when they wish to leave the shoreline and get out to the zone just beyond the breaking waves.
Summer is drawing to a close. If you made it to the beach this year, you managed to get your tan on and survive a shark attack. Congratulations! But there is another swimming danger that you should be aware of and that is moving into its most dangerous season: the riptide.
Riptides (properly called rip currents as they’re not actually a tide), are long, narrow channels of water which move from shore to sea and can take you with them as they go. They’re much more common during hurricane season, and especially the peak of hurricane season which is August until October.
80% of all open water rescue attempts are due to riptides, and they claim over 100 victims a year. So here’s a primer on what a rip current is, how to spot one, and how to survive if you get picked up and taken for a ride.
What Is a Rip Current?
Rip currents are channels of water which flow away from the shore and out to sea. As waves come into the shore, water piles up and needs somewhere to go. Instead of returning over the reef or sandbar from which it came, the current may take the path of least resistance and be funneled into a channel between two obstacles. Here’s a handy diagram and a more technical explanation from the NOAA:
- Waves break on the sand bars before they break in the channel area.
- Wave breaking causes an increase in water level over the bars relative to the channel level.
- A pressure gradient is created due to the higher water level over the bars.
- This pressure gradient drives a current alongshore (the feeder current).
- The longshore currents converge and turn seaward, flowing through the low area or channel between the sand bars.
There are three kinds of rips:
Flash rip: A rip current can form suddenly and vanish just as fast due to decreasing water levels or increasing wave heights.
Fixed rip: A fixed rip, sometimes formed between sand bars, can stay in the same place for days, weeks, or even months.
Permanent Rip: In a place with a permanent obstacle like a reef, a rip may be ever present.
How to Spot a Rip Current
Riptides can occur anywhere there are breaking waves, including large lakes. Spotting a rip current is not always easy, especially to the untrained eye. So be sure to heed warnings that are posted and issued by lifeguards and the like.
Here are some things to look for along with pictures from the University of Delaware:
A channel of churning, foaming, or choppy water
A rip current will pick up things like seaweed, forming a debris conga line which moves steadily seaward
In addition to debris, the rip current picks and stirs up sand, so look for areas of the water that are a different color than the surrounding water
A break in the incoming wave pattern
How to Escape a Rip Current
As mentioned, a rip current can suddenly appear. They can also rapidly ramp up in velocity. A rip current moving at 1-2 feet per second is no cause for alarm. But it can quickly start to move at a more dangerous 3 feet per second and have even been clocked trucking along at 8 feet per second.
If you get caught in a riptide, here’s what to do:
Don’t panic. Feeling like you’re getting swept out to sea can be terrifying. But try to keep calm. Rip currents won’t pull you under — they’re just channels of moving water. And while they can extend a ways out, they do eventually dissipate, most within 50-100 feet of the shoreline. So you’re not going to wash up on the shores of a deserted island with only a volleyball for a friend.
Don’t try to swim against the rip. Deaths that result from riptides aren’t caused by the current pulling someone under; instead, the person typically panics, starts trying to swim against the rip to get back to shore, becomes exhausted, and drowns. An 8-feet-per-second riptide is so strong that not even Michael Phelps, even when he had that amazing mustache, could swim against it. Don’t kick against the pricks.
Swim parallel to the shore. Instead of swimming against the rip current, you want to swimperpendicular to it, in either direction. Rip currents are typically only 20-100 feet wide. Once you leave the rip, swim at an angle away from it towards the shore.
Go with the flow. If you don’t have the swimming skills or energy to swim out of the rip, float on your back and go with the current. Just imagine you’re taking a spin on the Lazy River at the water park you went to as a kid. Once the rip current dissipates, you can do the parallel swim thing or try to signal to the lifeguard or someone else that you’re in need of help.