Alfred and his homemade submarine venture into the Southern Ocean. In Australia he's accused of sabotaging an oil tanker, which forces him to escape to Tasmania. There he meets Merwin Hughes, an eccentric environmentalist, and they travel south together. They're followed by a friendly blue whale and her calf. When Captain Paul Watson arrives aboard the Sea Shepherd Society's flagship to stop whalers, Al must try to save the mother and calf as he helps Watson fight off the whalers.