A group of young adventurers uses radio technology to mount a maritime expedition in search of sunken treasure, embarking on daring rescues and long voyages. Along the way they endure shipwrecks, marooning, undersea excursions, attacks by tentacled sea creatures, storms, mutiny, and volcanic disturbances that reshape their surroundings. The plot alternates technical ingenuity, survival challenges, and treasure-hunting suspense, resolving with the recovery of valuables and the reestablishment of order.