No, the cook is not going to start up the reactor or the backup diesel nor is he (or she!) going to bring the motor generators on line or start the evaporator or shift ballast or take a satellite fix or send a flash message or identify sonar contacts. Fight an engine room fire, sure. Handle trash disposal, coordinate stores, drive the boat on occasion, stand lookout and cook great meals, all in a day's work. Modern submarines are insanely complex. With all the training required, most sailors are E-4's before ever setting foot on one.