A Master Mariner or MM is the professional qualification required for someone to serve as the person in charge or person in command of a commercial vessel. In England, the term Master Mariner has been in use at least since the 13th century, reflecting the fact that in guild or livery company terms, such a person was a master craftsman in this specific profession (e.g. Master Carpenter, Master Blacksmith, etc. [1]). In the United States, the term was introduced in the mid-19th century.