Energy can be obtained from non-renewable sources of energy such as coal, oil, natural gas and renewable sources of energy such as wind energy, solar, Ocean and river. The energy of the ocean and the sea is the energy that contains the sea waves, currents, tides, tides, and energy that is a consequence of water salinity and temperature differences. Technology to take full advantage of the power of the ocean and the sea is still in development. The biggest reason for her neiskorištavanja are the big cost of building power plants. The energy of the sea and the oceans the most used to obtain electricity. To tidal energy and flow of the tides, waves and ocean currents could use needs to have certain characteristics (for example, the area of the height of the waves, which can be used). This paper presents the principles of operation of power plants that use the energy of the oceans and seas and the specified examples built power plants. Technology of exploiting the energy of the ocean and has intensified in the last few years developing.