What is a rip current? 

Rip currents are currents of water flowing away from the shore at surf beaches. They typically extend from near the shoreline, through the surf zone and past the line of breaking waves. The surf zone is the area between the high tide level on the beach to the seaward side of breaking waves.

What is undertow? Do rip currents pull people underwater?

There is disagreement among coastal scientists on the existence of a nearshore process called undertow, and hence there is not an agreed on definition for this word. Undertow is a term often and incorrectly used for rip currents. The best explanation for what many people attribute to undertow is as follows: After a wave breaks and runs up the beach, most of the water flows seaward; this "backwash" of water can trip waders, move them seaward, and make them susceptible to immersion from the next incoming wave; however, there is no surf zone force that pulls people under the water.

Why do some people use terms like runouts and rip tides when you are calling them rip currents? These terms, though once commonly used in certain regions, are now considered incorrect. The National Weather Service, Sea Grant, and the USLA are working together to use consistent terminology to provide a clear rip current safety message to the public.

What happens to people caught in a rip current? 

People get in trouble when they are moved so far offshore that they are unable to get back to the beach because of fear, panic, exhaustion, or lack of swimming skills.

Are all rip currents dangerous? 

Rip currents are present on many beaches every day of the year, but they are usually too slow to be dangerous to beachgoers. Certain wave, tide and beach shape conditions can increase rip currents to dangerous speeds.

How do rip currents form? Rip currents are formed when waves break near the shoreline, piling up water between the breaking waves and the beach. One of the ways that this water returns to sea is to form a rip current, a narrow jet of water moving swiftly away from shore, roughly perpendicular to the shoreline.

How big are rip currents? 

Rip currents can be as narrow as 10 or 20 feet in width though some may be up to 10 times wider. The length of the rip current also varies. Rip currents begin to slow down as they move offshore, beyond the breaking waves, but sometimes extend for hundreds of feet beyond the surf zone.

How fast are rip currents? 

Rip current speeds can vary. Sometimes they are too slow to be considered dangerous. However, under certain wave, tide and beach conditions the speeds can quickly become dangerous. Rip currents have been measured to exceed 5 mph, slower than you can run but faster than you or even an Olympic swimmer can swim. In some cases they have been measured as fast as 8 feet per second. This is faster than the speed at which an Olympic swimmer can swim a 50-meter sprint. Under most tide and sea conditions rip currents are relatively slow. However, under certain wave, tide, and beach profile conditions the speeds can quickly increase to become dangerous to anyone entering the surf. The strength and speed of a rip current will likely increase as wave height and wave period increase.

Where should I look for rip currents?

Rip currents most typically form at low spots or breaks in sandbars, and also near structures such as groins, jetties and piers. Rip currents can occur at any beach with breaking waves, including the Great Lakes and Gulf of Mexico. Rip current can be difficult for the average beachgoer to identify. Look for differences in the water color, water motion, incoming wave shape or breaking point compared to adjacent conditions. Look for any of these clues:

Channel of churning, choppy water

Area having a notable difference in water color

Line of foam, seaweed, or debris moving steadily seaward

Break in the incoming wave pattern

One, all or none of these clues may be visible.

https://www.weather.gov/safety/ripcurrent-faqs