In this rousing sequel to Three Against The Stars, Sergeants Seamus O'Hara, Claudia Akira, Fernando Cortez and a platoon of Marines are deployed to Canis-9 - Devoora, the Ocean Planet. Their mission: find seven indestructible robot warriors hidden there for seventy years. Most of the platoon survives a crash-landing but are left stranded in a hostile environment of deadly sea predators. Rescued by native Tulavi islanders, the Marines get caught up...