First why not further out:
* If in a platform with legs on or into the bottom, need shallow water.
* If moored with anchors, can go deeper, but still not in the bleak deep ocean which tends to be thousands of feet deep and not practical for anchoring.
* Have to get the power ashore. That means cable usually buried in the bottom. The shorter the better both from an initial cost and a maintenance perspective and for lowest power losses.
By the way, most fisheries, with the exception of deep water pelagics like bluefin tuna, occur close to shore in shallow water where sun reaches down and plants grow. This means trouble in wind power siting.
Now why not closer to shore:
* Important people do not want their ocean view taken (Kennedy family, wind farm proposal in Nantucket Sound).
* When waves come into shallow water they slow down and get much steeper until they break.
* Usually much steadier wind further from mountains and castles.
* Less interference with other shore uses.
Why would the Task Force recommend that the wind farm be placed 10 nautical miles off the coast?
2 answers
By the way, even pelagic fish tend to come in to shallow banks to feed because that is where the food is.