From audible.com:

In the 21st century, the United States has all but used up its oil supply. A new source must be found. Our atomic subtugs begin stealing oil from underwater deposits in enemy territory. But none of the last 20 tugs sent to bring back the desperately needed mineral have returned. Ensign John Ramsey of the Bureau of Psychology is planted aboard the Fenian Ram S1881 as an electronics officer. His assignment: find the saboteur in the four-man crew and bring back the oil.