Rip currents, riptides and undertow have different names because they're different phenomena. Rip currents are strong, narrow jets of water that move away from the beach and into the ocean. They can flow quickly, typically around 5 miles (8 kilometers) per hour; they aren't predictable and are a result of the shape of the coastline. A riptide is caused by the moon's gravitational pull and is a predictable rise and fall of the water level. Undertows are currents that pull you underwater to the bottom of the ocean.
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