Maybe you should have a look at this thread to get an idea what is entailed in the development of offshore wind farms: Offshore Wind Farms
As for FLOATING windmills there are only one commercial operation so far, the Hywind Wind farm off Scotland. The wind mills were assembled in a deep fjord in Norway by one of the world’s biggest SSCV the Saipem 7000 and towed to the site in upright position. Here is an article and video of the process FYI:
https://www.carbonbrief.org/qa-how-viable-are-floating-offshore-windfarms
It has been in operation since last Oct. and has proven more efficient than originally anticipated:
Walk-to-Work Offshore Wind Farm Service Operation Vessels (SOV) are not any old fishing boat, crew boat or even OSV. Here is one that is purpose built for the task:
PS> Long Pacific swells cause very different problems from short 3 m. significant wave height in the North Sea,