How long can a submarine stay underwater without needing to resurface?
A modern, nuclear powered submarine is ONLY limited by the amount of food which can be brought aboard. . It is entirely possible, and routine, for ballistic missile submarines to make their entire three month (and sometimes longer) deployment underwater. Fast attack submarines can as well. . For longer periods, additional food stores can be brought aboard. And the Ohio class SSBNs and SSGNs can effectively double their food stores, if required, which would extend their underwater capabilities to six months. . The ship provides all other needs: oxygen and potable water from the ocean water, electric power from the nuclear reactor.
