An unscrupulous local fisherman, Dorrie Stone, accidentally observes how Sandy and Bud Ricks are able to summon Flipper by sounding their ancient auto horn.
Old sea-lubber Hap Gorman fascinates young Bud Ricks with his tall tales of ocean bravery and the boy is convinced that Hap must be the most heroic man alive.
While Sandy and Bud prepare for the annual Coral Key Park swimming race, Porter is overcome by toxic chemicals dropped from a passing ship while he is carrying on an underwater investigation.
Bud, trying to help an injured man and his wife marooned on a sailboat, has to call desperately for help from Flipper when the boat becomes caught in treacherous coral reefs.
