A mysterious anomaly occurs off the coast of Cuba — a huge water tornado draws in water, draining the ocean. Belka and Strelka are sent by the Soviet rules to the island of fraternal peoples with an intelligence mission. The old friends will see beauties of Cuban nature and the azure expanse to the ocean, and the underwater world shrouded in secrets. They have to go through a series of dangerous adventures that will not only lead them to unravel the Cuban anomaly, but also test their friendship.