Wave power uses the kinetic energy (movement) and potential energy of ocean waves as a resource. In principle this can be used to generate electricity. However, the practicalities of harnessing waves have proved difficult to overcome in a cost effective manner for this type of energy production to take off in the UK.
Those interested in wave power can find out more in this Physics World article: https://physicsworld.com/a/wave-energy-in-the-uk-is-it-dead/
Wave power is commonly confused with tidal power which is actually a significantly different technology.