The energy from the oceans can be obtained mainly in three forms:

a) Tidal energy

b) Wave energy

c) Ocean thermal energy.

Some of the important limitations of these forms of energy are as below:

(i) Dams need to be built to harness tidal energy. Because the movement of tides in not constant in the ocean. Sometimes, there are high tides and sometimes low tides. Therefore, dams are necessary.

(ii) The wave energy can be harnessed in only at those places where the sea-waves are very strong. Moreover, setting up such systems is highly costly and require maintenance.

(iii) The efficiency of OTEC power plants which work by utilizing ocean thermal energy is very low. Moreover, it is very expensive to establish OTEC power plants.