To expand upon the message from Harvel, you may be able to obtain the official military service record for your father, which would indicate the ships to which he was assigned, applicable dates, training, illnesses or injuries, any decorations or medals earned, etc. Please see this page from the Armed Guard website that I manage: http://armed-guard.com/searchmil.html. In particular see section A.1. Records of Individuals - U.S. Military. You will have to contact the National Personnel Records Center in St. Louis, MO, a facility operated by the U.S. Archives. Provide as much identifying information as possible about your father. The links on the web page noted above will take you to the necessary pages of the Records Center web site. There may be a fee for obtaining the information but the Records Center staff will not begin research without informing you of any charge.
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website