There are about 2.7 terawatts of energy generated by waves on the ocean. About 20% of those energy can be captured with the current technology. One of the technology is PowerBuoy. The rise and fall of the wave cause a generator in the buoy to spin, thus generate electricity.
For this game, 2 versions are provided; PB350 PowerBuoy and PB6000 PowerBuoy, each producing 350MWh & 6000MWh of electricity. In the real world, the output of a single unit is much less than this. The output for game versions were bumped up to make it practical for SC4.
Comparison between power plants:
More detail stats are in the ReadMe.
If the electricity doesn't reach the shore, you can use Connector Buoy. It doesn't generate power but like any other structure in SC4, it 'conducts' electricity. Plop this 1x1 lot every 5 tiles to channel the power across water.
Located at the bottom of Power Utilities menu.
Available in MaxisNite(default) [RB PowerBuoys.zip] and DarkNite [RB PowerBuoys DN.zip] nightlight versions. Both has no dependency.