You could also go the wave generator route
See here. The more waves, the better!
They can also be built closer to shore since they have much lower profiles, and waves are higher in shallow water. Have to keep them out of shipping lanes, though. I could see where a wave generator like this could have ballast tanks that would allow it to go down about a hundred feet in a really severe blow, and pop up again later. Could you do that with a windmill? Maybe you could, if designed right.
