Undersea Fleet — Frederik Pohl; Jack Williamson

MONSTERS OF THE DEEP...

Everyone at the Academy knew that sea serpents were, without doubt, silly superstitions. Everyone but David Craken, that is. This young cadet from Marinia had been born and raised four miles beneath the waves, and he knew that more than rich new fuel sources and precious stones lay in wait for the men who dared invade this last frontier.

But when David dived into the depths at thirteen hundred feet and disappeared--only to reappear, drifting offshore months later--his friend Jim Eden learned there was more truth to certain superstitions than he cared to believe. On a strange and hazardous journey, Jim and the men of the Sub-Sea Academy suddenly found themselves up against the dangerous creatures of the deep--and embroiled in a life-against-life adventure they would never forget!