I saw this as someone's high school science fair project. The student envisioned that waves would have pressure on the ocean bottom as they passed due to their weight due to their height. Therefore valves on inlet pipes could feed high pressure seawater to the inlet of a turbine while valves on outlet pipes would release water from the turbine to low pressure parts of the passing waves. The system does not get in the way and has a low prifile for storms. The turbines could spin on a smooth flow of water. I'm impressed.
Aloha,
Charles M. Brown
i saw a while back a few prototype designs that were under serious consideration on "Beyond 2000" one is a water current mill, basically a wind mill underwater.
Another system was one that took advantage of waves as they came to the shore they filled the cavity of a chamber pushing air from inside it out through a turbine, as the water level fell air will suck into the chamber the turbines blades would change pitch causing the turbine to keep spinning in the same direction regardless of the wave moving up and down.
In a simple format the machine probably wouldn't work. BUT, if it were allowed to have a standing pipe which sticks out of the surface and 'catches' a wave, not letting the wave crest to move beyond it, then it could allow differential pressure to drive a turbine. I think using a "T" on top with a one way flap would capture the new water height and hold it until it all drained through the turbine. The "T" could be floated to stay even with the changing tides. This would capture a small difference in water height and 'big' waves would make little difference unless you made several layers (stacked) of inlet valves to catch varying wave heights. Kudos to the kid with the project.
Then again... maybe I'm the one who needs a lesson in wave / turbine dynamics. :-[