The Undersea Trilogy is a series of three science fiction novels by American writers Frederik Pohl and Jack Williamson.

Galaxy reviewer Groff Conklin praised the novel's craft, but faulted its espousal of "the petrifying process that military academies put children through" and the "us-against-the-world" attitude it engendered.

David Craken, a firm believer in the existence of sea serpents, disappears in search of them only to reappear drifting offshore months later.

His friend Jim Eden and members of the Sub-Sea Academy retrace David's journey and soon run into the strange creatures that had been only mythical before.

[citation needed] Floyd C. Gale reviewed the book as follows: Frankly and honestly, a gee-whiz yarn, it reaches its target—youngsters—with plenty of mystery, action, and suspense.