An underwater city built by Mr Heel, a greedy developer, has alarmed the race of fish people known as "The Dolphin Tribe". They threaten war against the surface people if their undersea expansion doesn't end. When Dr Elefun and Astroboy agree to stop the developers, the conflict is abated, but only temporarily. Angered by Elefun's presumption and the Dolphin Tribe's demands, Mr Heel kidnaps "Finny", the son of the Dolphin king. Fighting breaks out and it is up to Astro and Elefun to set things right above and below the sea.

The Dolphin king declares war on the surface people when his son "Finny" disappears