State the forms in which energy stored in the oceans manifests itself. Which one of these is utilised in $OTEC$ systems?

(N/A) Energy manifests itself in the oceans in the following forms:
$(i)$ Tidal energy: Energy derived from the rise and fall of ocean tides.
$(ii)$ Ocean thermal energy: Energy derived from the temperature difference between the warm surface water and the cold deep-sea water.
$(iii)$ Wave energy: Energy derived from the movement of ocean waves.
Out of these,Ocean thermal energy is utilised in the $OTEC$ (Ocean Thermal Energy Conversion) systems.