First and foremost, swim between the flags. Observing this basic rule just may save your life!
What is a rip current?
A rip current is a strong jet of water that quickly flows away from shore. Swimmers who are caught in rip currents can get sucked away from safety at speeds of nearly ten feet per second—far too fast for you to try swimming back to the beach.
On a normal day, waves crash against the shore at an angle, allowing water to come in and flow back out with little more than a tug at your feet. Larger waves can knock you over and create a bigger tug back out to sea, but it's easy for most people to overcome the normal push and pull of the water.
It's when the waves crash perpendicular to the beach that we start running into problems.
Rip currents also provide visual cues for you to identify potential hazard zones before getting in the water.
One of the best visual identifiers of a rip current is to look out for gaps between the waves. The calmer gap between waves may look safer for you to play without worry about waves washing over your head or overtaking little Timmy, but a small patch of calm water in an otherwise choppy sea is often a rip current. One of these gaps is pictured below—the rip current is in between the two red arrows.
Look out for discolored water near the shore. Rip currents tend to drag large amounts of sand and sediment back out to sea with them, so many rip currents are easily identified by a noticeable jet of crud in the water extending away from the shore.
Rip currents are also common in areas with sand bars (both surface and submerged), piers, jetties, groins, and anything else that sticks out from the beach that could catch a longshore current and cause it to start flowing away from shore.
Now, rip currents don't pull you under the water like so many television shows use as a plot device; instead, they pull you away from shore very quickly. If you're ever caught in one, don't panic. You'll start drifting away from the shore and your first instinct will be to panic and try to swim back as quickly as possible. Even the best swimmers can't swim against a rip current—since you can't fight the power of the water, you have to be smarter than the water.
If you're a good swimmer and you find yourself getting pulled out to sea, you have to swim parallel to the beach so you can get out of the current. Once you escape the influence of the outbound water, you can start swimming back towards shore. If you're not able to swim out of the current, signal for help by waving (not flailing) your arms and calling out for help while you try to stay afloat. The current will eventually let up and you'll stop driving away from shore; by that point, it's a matter of being able to stay afloat long enough for help to arrive.
[Source: Dennis Mersereau]