"Boatheader" is a unique word that doesn't lend itself easily to synonyms. One possible alternative could be "boat captain," which conveys a similar sense of authority and expertise in piloting a watercraft. Other potential synonyms might include "skipper," "navigator," or "helmsman." These terms all suggest someone who is responsible for guiding a boat through the water, either for leisure or commercial purposes. However, none of them capture the precise meaning of "boatheader," which refers specifically to someone who manages the movement and distribution of goods via boat.