Hydro power can also be called tidal energy. Tidal energy is harnessed by putting a turbine underwater and the tides spin the blades. The people in Europe by the Atlantic and the coast of North America are now starting to harness this new form of energy. Tidal energy is a lot like wind power except the blades are underwater. But unlike wind power, the blades do not kill any animals. This is because only the tides rotate the blades, not added inertia. The turbines work like a dam but on a smaller scale. It is one of the best long-term renewable forms of energy. So how does it work? The barrage holds the water back and lets some water go and it moves the fan. This costs about 15 billion dollars.