An undertow is a strong current beneath the surface of the water that pulls away from the shore. When waves crash onto a beach, all that water has to go somewhere. While you see the waves rolling in on top, the undertow flows back out underneath, creating a powerful force you might not see but can definitely feel.

If you've ever stood in the ocean and felt your feet getting pulled out from under you, or felt like the sand was being sucked away beneath your toes, you've experienced undertow. It can be dangerous because it works against swimmers trying to get back to shore.

The word also describes any hidden force that works against you. A student might face the undertow of distraction when trying to focus on homework, or a team might feel the undertow of doubt after losing several games.