People are naturally drawn to the beach, whether it's to relax, exercise, explore or just splash around. We know the ocean can be dangerous, but we also tend to misjudge the risks, worrying about toothy threats like sharks while overlooking a much larger, more likely man-eater: the ocean itself.

Rip currents are "the leading surf hazard for all beachgoers," according to the U.S. National Oceanic and Atmospheric Administration. They're responsible for an estimated 80 percent of all rescues performed by beach lifeguards, as well as roughly 100 drowning deaths per year in the U.S. alone. Sharks, by comparison, kill fewer than 10 people worldwide in an average year.

Like sharks, however, some rip currents are escapable if you stay cool and know how to react. It's always better not to get caught by one, of course — and sometimes that means fleeing the sea completely, such as when an offshore hurricane generates especially powerful rips. But this natural phenomenon doesn't always need to be a deal-breaker for the beach. Just keep these tips in mind to help you escape rip currents and, more importantly, avoid them in the first place.

Cocoa Beach waves

Florida has more rip-current deaths than any other U.S. state, averaging 21 per year from 1999 to 2013. (Photo: Ricardo Mangual/Flickr)

1. Rip currents are like treadmills.

As new waves crash into a beach, the previous waves have to go somewhere — and their channeled flow back to sea is what causes rip currents. The size of the flow varies, but it eventually fades as it gets farther from shore. Rip currents usually move at about 1 to 2 feet per second, according to NOAA, but they can reach 8 feet per second, which is too fast even for an Olympic swimmer.

When a person drifts into such a powerful current, panic can spur a misguided effort to swim against it back to shore. That's like running on a treadmill, but more exhausting. Rather than resisting a rip current, the best way out is the same way you get off a treadmill: any direction but forward.

If you find yourself in a rip current, start by orienting yourself while you calmly tread water. Then swim parallel with the shore until you're outside the perpendicular rip. Head for areas with breaking waves, since that indicates water is flowing toward the beach. If you can't make progress, keep treading water and try to draw attention by waving your arms. And if you see someone else in this situation and can't find a lifeguard, NOAA suggests calling 911, throwing out a float and shouting instructions on how to escape. People often drown while trying to rescue someone else from a rip current.

rip currents

Illustration: NOAA

Despite a popular misconception, rip currents aren't the same as undertow, which pulls down instead of horizontally away from shore. There's also no such thing as "rip tide," a common misnomer.

2. Certain parts of beaches nurture rip currents.

Rip currents can occur at any beach with breaking waves, including lakes or oceans. These incoming waves often build sand bars near the beach, pushing up sand as more and more water collects between the bar and shore. This water eventually finds a gap in the sand bar or creates one, letting it rush back to sea through a narrow path. Rip currents are also known to develop under piers, along jetties and around other beach features that can create wave-free channels away from shore.

In the photo below, a rip current is squeezing through a gap in a sand bar. The yellow letters mark where displaced waves feed the current (A), the "neck" of the rip channel (B), and the "head" where the rip dissipates (C). Some rip currents end just past breaking waves like this, but others flow for hundreds of yards, NOAA warns. Watch for warning signs like channels of choppy water, differences in water color, breaks in wave patterns, and lines of foam or debris moving steadily out to sea.

rip current overhead view

Photo: NOAA

3. The water in a rip current can seem calm.

While studying rip currents at a beach in Florida, Texas A&M researcher Chris Hauser noticed groups of people spreading out beach blankets on the sand right in front of an active rip current — and even swimming in the rip channel. When he began asking them why they chose that spot, he realized most people thought it seemed safer because its waters were calmer than the breaking surf on either side.

Because rip currents flow near the surface, they can look deceptively safe, NOAA points out, especially compared with big, splashing waves. But the opposite is true, since breaking waves push swimmers toward shore and rip currents carry them away. "If we know that what people are looking for as hazards when they go to the beach are the heavy, breaking white waves, then there needs to be information out there that sometimes what you can't see can be more dangerous," Houser says.

In the photo below, for example, waves are breaking over a sand bar (A) and filling in a trough (B) between the bar and the beach. The calm-looking channel in the middle (C) may seem like an extension of the calm trough, but it's actually a rip current carrying water from the trough out to sea.

rip current

Photo: NOAA

4. Heed official warnings not to swim.

Although many normal rip currents are manageable, sometimes the ocean is just too angry for human company. That can happen when a big tropical cyclone is looming offshore, for example, churning up violent rip currents that may be too powerful for anyone to escape.

Tropical storms killed six people in the U.S. in 2009, according to NOAA, all drowned by rip currents or storm surges. And cyclones can create deadly surf even without getting close: In 2008, rip currents from Hurricane Bertha drowned three people in New Jersey while the storm was still 1,000 miles away. Bertha also prompted 1,500 lifeguard rescues during a single week in Ocean City, Maryland. Such experiences have at least raised awareness, though: Rip-current warnings before Hurricane Arthur in 2014 helped prevent the storm from causing deaths, even though it hit on Fourth of July weekend.

It may seem pointless to close beaches when a hurricane isn't making landfall, but rip currents should always be taken seriously. If meteorologists or public officials tell you not to swim, don't swim.

For more about rip currents, check out this in-depth video from New York Sea Grant:

Russell McLendon is science editor at MNN. Follow him on Twitter and Google+.

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