The ocean’s mechanical energy, bound up in tides and waves, can be converted to electrical energy.

Tides are the regular rise and fall of the ocean level due to the gravitational pull of the moon on the earth. As the moon moves in its orbit around the earth, it pulls the ocean up on the side of the earth facing the moon, raising sea level relative to inland bays and estuaries. This bulge in sea level is high tide. At high tide, seawater flows inland into coastal bays and estuaries. At low tide, as the ocean level falls, this water ebbs back out to sea.

Figure 8 Gravity causes tides The pull of the moon's gravity causes high tides in two place: directly below the moon and on the opposite side of the earth. Click anywhere to start or stop the animation.