Despite the fact that the Navy likes to use the term engineering and engineer a lot, I wouldn't say anyone onboard a submarine would qualify as an "engineer", even the Engineer Officer. The only people who are "Nuclear Engineers" are the guys working at Naval Reactors or shipyards that do design work, testing, or other analysis. The officers onboard ship/submarine aren't engineers, they're technical managers/operators. Even the NRRO representatives aren't really engineers. If you want a professional title as an engineer, you'll most likely need at least a 4 year degree.