Ocean waves are caused by the wind as it blows across the sea.  Waves are a powerful source of energy. The problem is that it's not easy to harness this energy and convert it into electricity in large amounts.

Water wave energy is a source of energy obtained from waves on the sea surface .
It can be used to perform certain tasks: to generate electricity, to  freshen sea water and pump  it into reservoirs.

A presentation about wave power energy held by the Lithuanian students.