Even though the technology has not been adopted on a large scale yet, this form of energy has a high potential for a high yield, low cost alternative to conventional energy sources. Since 70% of the earth’s surface is covered in water, the ocean is an untapped resource whose energy is immense. Studies suggest that under current conditions, it would only take .2% of available ocean space to satisfy global energy needs. With Hydropower there are two main examples that are covered. The first is Tidal Power. The energy is created from the gravitational pull of the sun and the moon. Our tides are constant and limitless. The energy is harvested by submerging units that have turbines that are turned by underwater currents much like a windmill on land. Using the ocean’s natural currents, which are governed by gravitational forces from the sun and the moon, to turn the turbines produces a higher yield of energy than air. The reason for this is that the larger turbines used for wind power require larger surface areas to obtain the same output, whereas the ocean currents and the density of the water push smaller turbines to produce more energy. Strength of this technology lies in the ability to predict currents and where to place underwater “Turbine Farms” where the energy produced can be harvested. Previously this technology had been very expensive to implement but with new advances in the design and turbine technology it has the potential to be a viable source of abundant energy. Environmentally, Tidal Power is very clean as it does not require fuel, does not produce waste and is all but invisible. By placing the units on the floor of the ocean this does not cause interference with established sea route usage or marine life. The second source of Hydropower covered is Wave Power. These units sit on top of the water of the ocean and harvest energy by using a cylinder and piston like apparatus. Generally the unit has a buoy component and an anchor. The motion of the naturally occurring waves moves the buoy up and down causing the piston to push and pull air across a turbine. This too is a predictable source of energy since the currents can be watched and the devices can be put into optimal positions.