People living at a seashore town are frightened by reports of an unknown creature called "the sea devil". Nobody knows what it is, but it's really the son of doctor Salvator. The doctor performed surgery on his son and now young Ichtiander can live under water. This gives him certain advantages, but also creates a lot of problems.
A World War II era Soviet war film, focusing on the role of the Red Navy rather than land forces, and reviving the 1920s concept of the collective hero.
