I came up with an idea to generate electricity from ocean waves, and was wondering how it compares to other methods. Basically there is a heavy floating vessel riding the wave, and a steel rod attached to it going down to the seafloor. At the seafloor there is a vertical hydraulic cylinder with a length equal to the ocean wave amplitude. The steel rod is connected to the piston of the hydraulic cylinder, and the up and down action of the waves run a rotary hydraulic motor using the up down action of the piston. This hydraulic motor shaft is attached to an electrical generator. There are a couple more details too like a rod guide above the cylinder to keep the piston aligned, and a concrete base around the cylinder to make the devices deployable by ship.
Also since this is an electronics newsgroup, here's an electrical analogy: the waves are the voltage signal and the seafloor is the circuit ground, and the load is the hydraulic fluid movement :) Higher voltages (wave amplitude) equals more power!