The vast majority of U.S. aquaculture, the practice of raising and harvesting fish in controlled settings, takes place in coastal waters or on land, in tanks and ponds. But New Hampshire-based Blue Water Fisheries wants to place 40 submersible fish pens in water about 7.5 miles (12 kilometers) off Newburyport, Massachusetts, on two sites that total nearly a square mile, according to federal documents reviewed by The Associated Press.