There are patterns in the way that water moves toward the shore, and also patterns in the way that water returns to the sea. This backwash is most commonly felt as a broad sheet of water along the bottom. But sometimes water takes a much more dangerous route back - in localized channels called rip currents. These are narrow, swift flows of water that pose a serious hazard to swimmers.

Though rip currents can form anytime, they're more of a problem during storms, when waves are larger and lots of water is thrown toward shore. The incoming waves create underwater sandbars, and water starts to pile up between these sandbars and the beach. When breaks form in the sandbars, water is quickly funneled through, creating fast-moving rip currents out to sea.

These rip currents are often so strong that trying to swim back to shore against them only tires you out. Instead, first try swimming parallel to shore. Eventually, you should get out of the rip current, and be able to swim back to safety.