The nautical know-how you need to make marine a lucrative part of your business. With spring upon us, the thoughts of many who live in America’s colder climes turn to the water, and in particular, to boating. In 2013, some 88.5 million of the 242 million adults living in the United States — about 37 percent — engaged in fishing, sailing or other recreational watercraft uses at least once, according to the National Marine Manufacturers Association’s 2013 Statistical Abstract for Recreational Boating. The organization estimates almost 16 million recreational boats were in use that year.