A monster aboard the Sea View threatens to kill everyone.
The island of Mercora is sunk!
Captain Crane tries to stop a calamity.
The actors talk about how they did the rock and roll to simulate the boat.
As two escaped convicts plot to hijack the Flying Sub, the Seaview is menaced by a monster from the deep.
Captain Crane joins the crew of the Seaview and races to the North Pole to detonate a nuclear device in order to counteract the potentially deadly effects of massive tidal waves.
When the Van Allen radiation belt catches fire, Nelson’s plan to extinguish the blaze is thwarted by a misguided U.N. official.
At the behest of a brilliant scientist, Nelson and the crew investigate a fissure in the Earth’s crust which causes nearby sea creatures—and the scientist—to grow to gargantuan proportions.
While investigating a secret Soviet nuclear reactor, Nelson is injected with a substance turning him into a human time bomb, and it’s up to Crane to save the day.
The crew of the Seaview travels to the North Sea, where they must battle a sea monster and stop the evil scientist who created it.
Two Soviet scientists are rushed to disarm a defective atomic satellite which has crashed off the coast of California.
After Nelson's experimental submarine is attacked by a giant jellyfish, tension mounts aboard the Seaview as Nelson exhibits signs of a mental breakdown.
Nelson's sister is abducted by enemy agents who demand top-secret information as ransom, but will Nelson betray his country in order to protect the only family he has?
With Crane being held hostage, Nelson leads the fight against a sinister foreign power intent on stealing undersea defense missiles.
In the absence of Admiral Nelson, Admiral Park takes his place as a crazed scientist creates a giant, menacing creature that is half-man and half-fish.
In order to retrieve and disarm a lethal proton bomb, Crane must team up with a brilliant scientist who long ago defected to an enemy power.