What are the limitations of the energy that can be obtained from the oceans?

Explanation

The forms of energy obtained from the ocean are tidal energy wave energy, and ocean thermal energy. There are several limitations to harness these energies.
(i) dal energy depends on the relative positioning of the earth, moon, and the sun.
(ii) High dams are required to be built to convert tidal energy into electricity.
(iii) Very strong waves are required to obtain electricity from wave energy.
(iv) To harness ocean thermal energy effliciently, the difference in the temperature of surface water [hot) and the water at depth [cold] must be `20^(@)` C or more.