Oceans give us a lot more than seafood and salt. Besides giving us food, the ocean provides oil, fertilizers, and food for farm animals. Some ocean water is purified to yield freshwater.
The ocean also produces waterpower. In some places, the tides are strong enough to run generators. For instance, in the Rance Estuary in France, there is a row of 24 tunnels. Each tunnel contains a turbine, which is designed like a fan. When the blades are turned, electricity is generated. So when the rising and falling tide pushes water through the tunnels, it turns the turbines and generates power.
Waterpower is important because it does not use up resources that take a long time to replace, such as coal and petroleum.
