Simply stated, The Merchant Marine is the U. S. Merchant Fleet. During World War II Merchant Mariners manned the ships that transported men and supplies to the various points of the compass. Ships and men were non-military but U. S. Navy Personnel provided gun crews. The Merchant Marine Academy has a website at < http://www.usmma.edu/http://www.usmma.edu/ >. If your man was an officer there's a better-than-even chance he's a graduate and they'll have some record of him.