What is tidal energy ? How is it harnessed ?

Explanation

As is known, hydropower is the least expensive way to generate electricity, and that too with least pollution problems caused by burning coal and oil to produce electricity.
Twice each day, the Atlantic Ocean pours into the Bay of Fundy (in eastern Canada) producint the highest tides in the world ranging rom 12m to an extreme of 17m. The huge amount of kinetic energy available in these tides can be converted into electrical energy by building a dam and hydroelectric power plant at the entrance to the bay.
Such a dam would obstruct the natural flow of tides. Every twelve hours, the incoming tides will rush through the open flood gates in the dam and be impounded behind the dam.
When the tides recede, water would exit through turbines generating hydroelectric power.