Episode list

Chip Morton and Curley Jones are in New London making repairs on the diving bell's guidance system. At the same time a skirmish in the control room of the Seaview inadvertently allows it to move into a derelict mine field. The sub becomes entangled and attempts to free itself, but an explosion disables the sub and sends it to the bottom. With the crew running out of air the diving bell is their only hope.

A U. F. O. has been spotted flying around the United States, terrifying people and violating every airspace regulation in the book. It falls into the sea, which, after another ship is destroyed investigating it, the Seaview is ordered to check it out.

Nelson is told the Seaview could be destroyed while carrying a top secret defense weapon but he has to determine if Captain Crane is an impostor.

The Seaview is on exercises when a series of signals are received indicating the USA is at war and they are to prepare for launch of all missiles.

After the arrival of a newly elected U.S. Senator to inspect Admiral Nelson's new weapon, strange things begin to happen, culminating with the realization that everyone outside of the Seaview appears to have disappeared from the Earth.

Admiral Nelson and Captain Crane are shocked to see a scientist shot to death during a live televised news conference viewed from the Nelson Institute. Especially shocking is that the killer appears to be Admiral Nelson. Both Nelson and Crane are eventually able to overcome efforts to stop them from boarding the Seaview. The submarine races to stop an earth-threatening project set in motion by the radical scientist, who may not really be dead after all. In the meantime, a very dangerous master of disguise causes mayhem and confusion as he tries to stop the Seaview from saving the world.

An unfriendly government shoots down a cargo plane carrying a new top secret bomb. The race is on to retrieve the bomb and avoid detection from the enemy before the bomb can be accidentally exploded.

While assisting an undersea drilling operation, Capt. Crane and the Seaview become locked in a life-and-death struggle with an android, powered by a new source of limitless energy, Subterranium 116.

Crane is brainwashed to sabotage an important national defense mission which is being monitored by the national intelligence agency.

When four capital ships vanish, Admiral Nelson and Commander Van Wyck are sent to investigate. They find an island where Nelson removes a dagger from a skeleton which happens to be the captain of the Amsterdammer, the Flying Dutchman, and is then cursed. Van Wyck is in reality the first mate who killed the Captain. His plan is to kill Nelson with the dagger so that he can be free and Nelson will take his place.