A savage killer whale blockades a strip of coastline, capsizing boats and harassing skin divers and swimmers. Mike Nelson, armed with a shark-harpoon gun, engages the killer whale in a wild and desperate undersea battle.
Mr. Marvello, a down-and-out ventriloquist thrown out of the Parkey Bros. Circus, wanders into Coral Key Park.
Three brothers hire Mike Nelson to give them SCUBA instructions. Their secret purpose for the lessons: a daring underwater attempt to free a fourth brother from Alcatraz, the 'unbreakable' island prison.
Things take an ominous turn for Sandy and Flipper when the plane carrying them to the Bahamas crashes in the ocean.
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.
