 Unlike the previous book by Lester Del Rey, this book is actually quite good. It's the typical 1950s style young boy hero plot. This young man's father invents and builds an experimental nuclear submarine and the kid gets to go on the maiden voyage because he understands the system better than anybody else and he manages to smuggle his trusty dog on board, which manages to save the day more than once. The descriptions of the underwater cities and the people who live in them are actually quite clever and Who could resist this cover painting? I mean, come on.