Erica's Answer:A rip current is a very fast – moving ocean flow, moving away from shore and out to sea. Undertow is not as severe an outward pull as a rip current, but when you experience undertow, you can feel the water near the ocean floor being pulled out to sea. This fast-moving ocean water pulls sand along with it, which is why your feet will get buried in the sand if you try to stand still in a strong undertow situation! Rip currents can be deadly and should be avoided at all times. Undertow can still be dangerous, but is much weaker, and therefore not as dangerous.