The term 'Builder Navy' refers to a group of people who are responsible for constructing ships and other vessels. The two crossword solutions for this term are INCA and NOAH, both of which are four letters long. INCA is an acronym for the International Naval Construction Association, which is an organization that provides training and certification for shipbuilders. NOAH is an acronym for the National Organization of American Harbors, which is a non-profit organization that works to promote safe and efficient harbor operations.