Not only offshore wind, but tidal streams and wave can be converted to usable power,
Here is a new tidal power station being readied in Nova Scotia, Canada:
Reviving this dormant thread:
Now let’s anybody will have any negative comments to this one. 
(No prize for guessing from who)
Never figured out why you can’t simply attach a Kort Nozzle type device to the legs of those ugly windmill type things that pollute our coast’s. You know for sure you are going to get water passing it at a decent rate for a guaranteed period of time. Around this area a good 4 kts of it for the main part of the tide.And you have a pretty good idea in which direction it is going to go. Unlike the windy mills that have to start the diesel engine and rotate the blades when they find themselves stopped facing the wrong direction.
The damn things are being installed anyway
Sorry that should be Nacelles not blades above
Most modern wind turbines are using power from the grid, or battery banks, to turn the nacelle into the wind:
"Large commercial wind turbines actually use an electric yaw motor powered by the grid (or backup generators/batteries) rather than an on-site diesel engine to turn the nacelle toward the wind.
Anemometers and wind vanes (or ultrasonic/LIDAR sensors) on top of the nacelle track changes in wind direction and send signals to control motors.
Traditional or smaller wind pumps often used a simple tail fin or a small secondary fantail to automatically steer themselves into the breeze".
Source: Variouse.
And what power’s those remote generators pray tell.
Wind power. The turbine is connected to a grid, which is interconnected within the cluster, to the offshore substation(s) and to shore grid.
If the entire field is down, the supplies comes from battery packs, either on individual nacelles, or on the offshore substation(s)
Batteries then ok
Just how many AA batteries does it need to turn a nacelle 90*
Or are these the massive gel batteries that need to be charged from those nice gas power stations with gas supplied by Norway?
Many.
No. They just collect surplus gas cannister, now that the grilling season is over.