The ocean as an energy source

Hydropower is one of the world already intensively used form of renewable Energy which is known to mankind for a long time.
The kinetic Energy of the water was centuries ago by the mills in mechanical energy converted.
Hydropower stations are being built for the production of electric energy in many rivers in the world.
The energy from the ocean has the potential for sustainable Generation of electrical energy, which so far is mostly untapped. On the far right locations in Europe and Asia are already Installations with a rated capacity of over 50,000 MW installed.
This represents only a fraction of the suspected global production potential of Ocean currents from around the world (800 TWH). The energy of the seas can be roughly divided into three groups:
Mechanical forms of energy (tidal power, wave power and Fluid power plants)
Thermal Energy (Ocean Thermal power plants)
Energy from differences in salinity (osmotic power plants)
the best reference for ocean energy (in german language)