Mr. Marvello, a down-and-out ventriloquist thrown out of the Parkey Bros. Circus, wanders into Coral Key Park.
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.
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.
Congresswoman Helen Browning comes to visit Coral Key Park and Marine Preserve to decide whether government funds should be appropriated to keep the park open.
When the State of Florida is plagued with a series of underwater crimes, Mike Nelson is called to organize and train an underwater police force.
