The Douglases fear Steve (Fred MacMurray) is becoming sedentary.
When Flipper finds a Spanish doubloon on the ocean bottom and brings it to Bud and Sandy, rumors about Spanish Treasures spread quickly and an underwater gold rush ensues.
Flipper goes to Bud and Porter Ricks for detective help after seeing a treasure chest stolen from the wreck of a sunken Spanish ship and hidden on a nearby island.