List and describe four approaches for obtaining energy from ocean water

1. Tidal energy - By erecting dams across outlets of tidal basins, as currents pass through the dam, water turns turbines to generate electricity

2. Wave energy - harness motion of waves and convert mechanical energy into electricity. This can be done by use of floating devices that move up and down by wave action that can push air into/out of chambers turning turbines.

3. Ocean currents - underwater wind turbines harnessing the powerful movement of deep cold ocean currents

4. Ocean Thermal Energy Conversion - warm surface water on the oceans can be piped into a facility to evaporate chemicals at low temperatures, these gases then spin turbines. Cold water will be used to condense these gases so they can be reused.