ABOARD THE USS NEW MEXICO—There are subcultures. And there are cultures aboard a sub.

Silently cruising the ocean depths while safely operating a 130-man tin can powered by a mini nuclear-power plant doesn't leave much room for error. That is why sub culture is built around rules, some dead serious, others completely ridiculous and some that are both.

There are rules to run the systems that provide the submarine's oxygen, water and power. And there are rules that keep the crew, whose bunks allow just 14 inches of headroom, somewhat sane.

One of the most important rules has every new junior officer teamed with a slightly more experienced officer who watches over the rookie, mentors him and corrects his mistakes. It can be a fractious relationship.

Under the hard stare of Lt. j.g. Josh Bergeron, the mentor, Lt. j.g. Tommy Plummer makes a habit of fumbling the basics, such as how to operate a radio, which on a sub is notoriously difficult.