A jetty is a long structure made of wood, concrete, or stone that extends out from the shore into a body of water. Picture a sturdy walkway or wall reaching out into a lake, river, or ocean, like a finger pointing into the water.

Jetties serve several purposes. In harbors and at river mouths, they protect boats from waves and currents, creating calmer water where ships can safely enter or leave. They also prevent sand and sediment from filling up shipping channels. At beaches, jetties help control erosion by slowing down how waves move sand along the shore.

People often walk out on jetties to fish, watch boats, or look out over the water. If you've ever stood at the end of a long pier watching waves crash against the rocks below, you might have been on a jetty. These structures have helped sailors and fishermen navigate coastlines for centuries, and they remain essential to ports and harbors around the world today.