Salter’s Duck
This device, invented in 1974 and the first of the wave power devices, is an egg-shaped device that moves with the motion of the waves. The device captures the motion of the waves and converts up to 90% of the wave energy into mechanical energy. Different versions of the Duck use slightly different methods to accomplish this, like a pendulum or rotor, to move a generator.
The video below, while old, provides a good overview of Salter’s Duck.