A huge iceberg calves that holds a megalodon (mega shark) and a giant octopus frozen inside it. Deployment of a LFAS (low frequency automatic sonar) unit causes it to shatter. The two behemoths thaw and return to life. The shark terrorizes the California coast while the octopus creates havoc things near Japan. A group of three oceanographers put together a plan to draw the beasts into a trap with pheromones.