Sandy Ricks saves a dolphin by pulling a spear out of his side. But his father Porter, a fisherman, insists on releasing the dolphin, especially after the dolphin eats his entire catch for a day. But the dolphin returns the favor when Sandy, snorkel diving to replace the consumed catch, comes under attack by sharks.
Fisherman Porter Ricks faces the destruction of his way of life with the coming of the Florida Keys Causeway. At the same time, his son Sandy and his newfound dolphin friend Flipper are in the Bahamas, where they tangle with three escaped convict/pirates who take an English family hostage.
After witnessing all the marine animals fleeing the area, Bud and Sandy alert the local folk of a hurricane headed their way, despite their father's instructions and a clear weather forecast. No such hurricane eventuates and believing they have wasted time and money in securing their boats, the towns people look to Porter for compensation. It is only after a tidal wave hits that everyone in the town is grateful to Flipper and the boys for the warning.