Season 1
Episode: 1x01 | Airdate: Sep 14, 1964
A gigantic tidal wave will destroy much of the civilized world, but Admiral Harriman Nelson has a plan to stop it -- Seaview will set off a nuclear explosion at precisely the right time and place. Evil forces seek to destroy Nelson before he implements his plan -- in the chaos following the tidal wave, they hope to take over the world! Seaview's original Skipper is killed and it's Lee Crane from the US Navy to the rescue.
Episode: 1x02 | Airdate: Sep 21, 1964
While investigating the disappearance of research ships in the Aegean, the Seaview is damaged by a bomb. Captain Crane goes ashore, and pretends to be a diver for hire. The Captain meets an ex-diver, now a mute due to a tragic accident, who claims to have seen a "city beneath the sea". Crane gets hired by the "bad guy", but his cover is soon blown. He is taken prisoner and nearly loses his life.
Episode: 1x03 | Airdate: Sep 28, 1964
After Seaview's sister ship, Polidor, is lost on an experimental deep dive, Seaview continues with the tests. Unknown to the already stressed crew, one of the visiting psychologists aboard is an enemy agent who has released a fear-causing gas into the air system. As Seaview plunges into the depths a dangerous panic starts to spread.
Episode: 1x04 | Airdate: Oct 5, 1964
On a rendezvous mission, Crane and several crewmen are drugged into unconsciousness on a deserted yacht. Waking up in a South American prison, the men are taken out to the courtyard, one per hour, and executed. All will die unless Crane breaks his oath and confesses what he cannot. Will Nelson's rescue mission succeed? Will the country in question survive the machinations of the evil man who wants to take over?
Episode: 1x05 | Airdate: Oct 12, 1964
A husband and wife Antarctic research team is killed by an experiment on plankton gone wild. Seaview arrives to investigate and take plankton samples. Soon the submarine is in danger of succumbing to the horrible, slimy growth. Nelson, Crane and crew face another problem: one of the three scientists on board the sub is an enemy agent.
Episode: 1x06 | Airdate: Oct 19, 1964
An alien spaceship lands in the ocean, and Seaview is sent to investigate. Although Seaview is powerless in the vicinity of their ship, the aliens seem friendly, and Nelson manages to open negotiations. The military authorities, however, have other ideas, and Seaview may be in as much danger from human interference as from the aliens.
Episode: 1x07 | Airdate: Oct 26, 1964
A lush, tropical, verdant paradise in the South Pole? Living dinosaurs? Such fanciful ideas must surely be the ravings of a madman. Or perhaps not, as Admiral Nelson soon discovers. The question is, will he and Crane survive their trip to a lost world?
Episode: 1x08 | Airdate: Nov 2, 1964
A sea monster kills three villagers in a Norwegian fjord; however, one man survives. Seaview arrives to investigate. Nelson and Crane are met with hostility from the locals and find the survivor has died. Nelson does his best to make sure the "sea monster" doesn't destroy Seaview.
Episode: 1x09 | Airdate: Nov 9, 1964
A Soviet satellite has crashed into the sea and its nuclear reactor must be disarmed before it causes a disaster. Two Soviet scientists come aboard Seaview to carry out the work -- but one of them is an imposter.
Episode: 1x10 | Airdate: Nov 16, 1964
Damaged by an explosion from an old mine field, Seaview takes a dive to the ocean floor. Listing dangerously, running out of oxygen, having to deal with fire and flood, the crew can do nothing but wait for help. But will help arrive in time?
Episode: 1x11 | Airdate: Nov 23, 1964
A mysterious weapon is destroying American U2s. The Seaview's mission is to find the weapon and destroy it. Captain Crane goes undercover. A night-club performer, who is also a resistance fighter, comes to Crane's aid. The Captain is soon captured and severely beaten. Meanwhile, on Seaview, Major Amadi demands asylum. To prove his sincere intentions, he promises to lead the sub to the powerful magnetic weapon responsible for taking out those U2s. Nelson suspects he wants to lead Seaview to a watery grave.
Episode: 1x12 | Airdate: Nov 30, 1964
Nelson and Crane go undercover and risk their lives in order to bring a Communist defector back to the United States. But the man is injured in the attempt, and his lover is left behind. He won't speak to the agent waiting for him on Seaview (actually a double agent) until he is reunited with his Anna. But even Anna is not all she seems
Episode: 1x13 | Airdate: Dec 7, 1964
In blizzard-wracked Florida, Nelson contacts a meteorologist who may be able to help explain the strange weather conditions. That night, however, the scientist is abducted, and "programmed" to kill Nelson. When his first attempt fails, he comes aboard Seaview when she sails to investigate the source of the problem, and continues his efforts.
Episode: 1x14 | Airdate: Dec 14, 1964
An old friend of Nelson's comes aboard Seaview to continue his research into the giant whale that destroyed his ship, crippling him and killing his son. His real motives, however, have more to do with vengeance than science, and Crane becomes concerned that the Admiral is caught up in his friend's obsession.
Episode: 1x15 | Airdate: Dec 21, 1964
When the King of a small but friendly nation is assassinated, Seaview is assigned to take the young Crown Prince back home to assume his throne. Neither Nelson (who gets turned out of his own cabin) nor Crane are used to handling children. Help arrives in the form of a mysterious flute-playing old man who befriends the boy after he is picked up at sea.
Episode: 1x16 | Airdate: Dec 28, 1964
Injured in a fall, the President of the United States is in desperate need of surgery -- and the operation must be kept secret. Naturally, Seaview is chosen as the best place for the operation. An enemy agent, taking the place of the doctor who would have used a radiological device on the President, will attempt to kill the Commander-in-Chief with a deadly ray. Will she be discovered in time to save the President?
Episode: 1x17 | Airdate: Jan 4, 1965
Admiral Nelson is kidnapped by a group of German survivors of WW II who dream of establishing the Fourth Reich. They plan to use Nelson, along with a group of other kidnapped scientists, to bring this about.
Episode: 1x18 | Airdate: Jan 11, 1965
Admiral Nelson is aboard a new submarine when it is destroyed by a giant jellyfish. Nelson and the first officer are the only survivors. The two men begin a desperate battle for survival while being presumed lost at sea by the navy.
Episode: 1x19 | Airdate: Jan 18, 1965
When a mass missile launching by a foreign power sets the U.S. on nuclear alert, the Seaview goes into a fail-safe maneuver, but is the launch really what it appears to be, and does this actually mean it's "doomsday?"
Episode: 1x20 | Airdate: Jan 25, 1965
An undersea earthquake exhumes hundreds of strange metallic capsules, and a powerful humanoid creature who could destroy mankind is restored to life after millions of years in suspended animation.
Episode: 1x21 | Airdate: Feb 1, 1965
After returning from a mission in deep space, a lifelike robot is brought aboard the Seaview, but the crew soon discovers that the robot has been mysteriously reprogrammed to wreak havoc.
Episode: 1x22 | Airdate: Feb 8, 1965
A mad art connoisseur seizes control of the Seaview and plans to pirate Leonardo da Vinci's Mona Lisa from a French Ship bound for the World's Fair.
Episode: 1x23 | Airdate: Feb 15, 1965
The Seaview is selected to be converted to a totally automatic ship controlled by a central computer. The mission goes well till Capt. Crane, the only person aboard the sub, realizes he may not be as alone as he thought.
Episode: 1x24 | Airdate: Feb 22, 1965 (50 min)
Crane is brainwashed to sabotage an important national defense mission which is being monitored by the national intelligence agency.
Episode: 1x25 | Airdate: Mar 1, 1965 (50 min)
The Seaview is sent on a mission that will take into to some of the most dangerous waters in the world for submarines. Adding to the tension one of the officers lost an elder brother on a similar mission years before.
Episode: 1x26 | Airdate: Mar 8, 1965 (50 min)
Admiral Nelson becomes involved in a project to develop an amphibian adaption for man. He encounters conflict with the two chief scientists, rather than being cautious, both scientist want to rush ahead with research. Nelson worries what the emotional toll of the experiments may be.
Episode: 1x27 | Airdate: Mar 15, 1965 (50 min)
The premier of the "People's Republic", with some very valuable information, wants to defect to the US. The Seaview is sent to pick him up, but Nelson must first evaluate the information before deciding if the mission worth the risk.
Episode: 1x28 | Airdate: Mar 22, 1965 (50 min)
When a missile is destroyed by apparent ultrasonic sound, the Seaview investigates with Adams, the mentally unstable launch commander, on board and finds an giant manta ray source which along with Adams' actions pose a threat to safety.
Episode: 1x29 | Airdate: Mar 29, 1965
The Seaview is sent to investigate the wreck of the submarine Angler. They uncover evidence of strange behavior minutes before the loss, and Nelson sees this change in behavior as the secret to unlocking what happened to the Angler.
Episode: 1x30 | Airdate: Apr 5, 1965
Nelson is to meet a scientist working on a secret project at Loch Ness. When he arrives he discovers the scientist is dead. A series of strange events leads Nelson to believe there may be a way for a submarine to enter the Loch.
Episode: 1x31 | Airdate: Apr 12, 1965
This episode involves the testing of a new air mixture that will allow a submarine to go to the "bottom of the sea" literally! A brash, news hogging, admiral and his aide, along with his assistant all successfully make the first tests in a diving bell. Then it is time for the Seaview to follow suit. Only then does the real fun begin!
Episode: 1x32 | Airdate: Apr 19, 1965
Admiral Nelson is deeply concerned when he hears his sister has been kidnapped. He soon discovers she was not the real target and he is being placed in a position to have to go against everything he ever stood for.
Season 2
Episode: 2x01 | Airdate: Sep 19, 1965
The Seaview is on a joint mission with Russian scientists to salvage the remains of a Soviet undersea lab. While a scientist is being lowered in the diving bell, a giant whale arrives and rams the bell. The glass is shattered, killing him. Nelson and the remaining Russian scientist, Katya Markova, go on a second dive. The whale reappears, this time swallowing the diving bell whole! Now it's a race against thime as Captain Crane and the crew of the Seaview find the diving bell and get it out before Nelson and Markova run out of oxygen!
Episode: 2x02 | Airdate: Sep 26, 1965
The Chinese have developed a way to turn a human body into an intense bomb. They intend to infiltrate the Soviet Union and create a diplomatic incident that will draw the US and Soviets in nuclear annihilation.
Episode: 2x03 | Airdate: Oct 3, 1965
A message is received from a US sub presumed sunk in the last months of WW2. The Seaview is sent to try and locate a cave that is mentioned in the message and to try and rescue the 5 men believed to be still alive.
Episode: 2x04 | Airdate: Oct 17, 1965
Cybernetic genius Tabor Ulrich creates a perfect mechanical duplicate of Admiral Nelson. His plot: to make the crew of the Seaview think they are fighting World War Three. In doing so, the sub will launch nuclear missiles at the China, Russia and the USA. After the holocaust, Ulrich plans to take over and usher in "the age of the cyborg".
Episode: 2x05 | Airdate: Oct 24, 1965
Captain Crane is in Venice to meet a secret agent when she is killed. It is believed she had knowledge of a new secret Soviet weapon, and how to combat it. Crane's mission is made more complex when he is accused of the agents death.
Episode: 2x06 | Airdate: Oct 31, 1965
Admiral Nelson is contacted by an agent claiming to be from the Office Of Naval Intelligence. He gives Nelson a cryptic message that the current nominee must not be allowed to become Secretary of Defense, no matter what it takes.
Episode: 2x07 | Airdate: Nov 7, 1965
The President of the United States is visiting a new underwater installation when a power interruption freezes all communication. To complicate the situation they discover there is some sort of beam weapon stopping any of the safety over-ride mechanisms from activating.
Episode: 2x08 | Airdate: Nov 14, 1965
A research team are taking measurements of an underwater eruption. They discover a fissure that appears to lead all the way to the Earth's core. While the discovery is exciting, what exists in that fissure could lead to deadly consequences.
Episode: 2x09 | Airdate: Nov 21, 1965
Nelson and the Seaview witness the detonation of a new bomb developed by the Chinese. No bigger than a milk carton, it creates a blast 20 miles across. An American scientist who had defected to the other side steals it for his use.
Episode: 2x10 | Airdate: Nov 28, 1965 (50 min)
A manned probe is returning to Earth when it is suddenly caught in the grip of a strange force and destroyed. Investigations point to a secret Chinese installation being responsible. Capt Crane is tasked with locating the base and destroying it.
Episode: 2x11 | Airdate: Dec 5, 1965
Word comes through that Dr Liscomb has been kidnapped by a foreign agent posing as a toy importer. Liscomb has cracked the secret of the X factor, a new ingredient and everyone wants it.
Episode: 2x12 | Airdate: Dec 12, 1965
Admiral Nelson is under pressure when a drone sub system he pioneered malfunctions and fires three missiles at New York City. The race is on to establish what went wrong and how to stop it happening again
Episode: 2x13 | Airdate: Dec 19, 1965
In 1978, the first space probe to Saturn returns and the Seaview is sent to retrieve it. Despite their stringent decontamination procedures an alien life form survives and, once inside, begins to take over the ship.
Episode: 2x14 | Airdate: Dec 26, 1965
Admiral Nelson and Chief Starkey are marooned on an island with prehistoric creatures. The Seaview is trying to rescue them but they have an undersea monster of their own to contend with
Episode: 2x15 | Airdate: Jan 2, 1966 (50 min)
By air Nelson and Crane pursue a mysterious submarine stealing nuclear missiles. Their craft is shot down and Crane is captured. Nelson, recovered by a Navy destroyer, is bent on destroying the sub, not realizing Crane is on board.
Episode: 2x16 | Airdate: Jan 9, 1966
The Seaview rescues two men apparently lost at sea. They are actually escaped prisoners who try to take over the Seaview. The situation is complicated by the presence of a giant sea monster attacking the ship.
Episode: 2x17 | Airdate: Jan 16, 1966 (50 min)
The Seaview finds a sunken German U-boat while mapping the ocean floor. Sunk during WWI in the north Atlantic, it is now somehow in the south Pacific. Its captain boards the Seaview with Capt. Crane as his prey.
Episode: 2x18 | Airdate: Jan 23, 1966 (50 min)
A meteor storm ignites atmospheric gases in the southern hemisphere. Adm. Nelson believes one of the Seaview's missiles can extinguish it but someone on board is secretly trying to stop him.
Episode: 2x19 | Airdate: Jan 30, 1966 (50 min)
The Seaview is returning to the location of a sunken ship to recover its secret cargo. There are a number of other sunken ships in the area, and the thing responsible for all of them soon threatens the Seaview.
Episode: 2x20 | Airdate: Feb 6, 1966 (50 min)
The construction of an undersea canal is about to start with the Seaview tasked with placing the first charge, a 50 megaton nuclear bomb. But as it is being lowered an enormous whale swallows it and swims off.
Episode: 2x21 | Airdate: Feb 13, 1966 (50 min)
While operating over the remains of a sunken 16th century pirate ship, the Seaview encounters a reincarnation of its dead captain.
Episode: 2x22 | Airdate: Feb 20, 1966 (50 min)
Everyone but Nelson and Crane are removed from the Seaview and replaced by 8 civilians to test new equipment. One of them is a foreign agent who wants to kill everyone on board and use the ship to provoke an incident and start a war..
Episode: 2x23 | Airdate: Feb 27, 1966 (50 min)
A test submarine carrying a load of experimental fuel is disabled and lying on the ocean floor. The Seaview is sent to recover the volatile fuel canisters but an enormous underwater spider threatens to destroy them.
Episode: 2x24 | Airdate: Mar 6, 1966
While Adm. Nelson is away, Capt. Crane tries to prevent Dr. Borgman from implanting human DNA into marine animals to create a new type of undersea creature.
Episode: 2x25 | Airdate: Mar 13, 1966
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.
Episode: 2x26 | Airdate: Mar 20, 1966 (50 min)
Captain Krueger returns and once again wants Captain Crane's body. He threatens to kill everyone on the Seaview if Admiral Nelson doesn't shoot Crane and deliver his body to him.
Season 3
Episode: 3x01 | Airdate: Sep 18, 1966
A strange intelligent organism is found at the bottom of the ocean. Once brought on Seaview the real threat the creature represents is realized. Suddenly every life on board the Seaview is in danger.
Episode: 3x02 | Airdate: Sep 25, 1966
Scientists on a tropical island are measuring the radioactivity of a volcano when they are attacked by a wolf. Prof. Hollis shows signs of lycanthropy and threatens everyone on board, especially Admiral Nelson, whom he has infected.
Episode: 3x03 | Airdate: Oct 2, 1966
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.
Episode: 3x04 | Airdate: Oct 9, 1966
The Seaview's diving bell is driven by a tsunami onto a tropical island where a mysterious mist causes the survivors to see imaginary people and creatures.
Episode: 3x05 | Airdate: Oct 16, 1966
An old man, adrift at sea, is rescued along with a sack of toys by the Seaview. The toys take on a life of their own and begin to sabotage the ship. The toys appear to be connected to an alien space ship lying on the ocean floor.
Episode: 3x06 | Airdate: Oct 23, 1966
An alien being, capable of impersonating any member of the crew, gets on board the Seaview. He plans to use the Seaview's missiles to start a nuclear war and thereby make the Earth ready for conquest.
Episode: 3x07 | Airdate: Oct 30, 1966
An emergency mission leads the Seaview to rescue Kowalski's brother Stan. Once on board, Stan's refusal to help anyone else threatens the sub's survival after it sinks to the ocean floor, a thousand feet below it's crush limit.
Episode: 3x08 | Airdate: Nov 6, 1966
A controversial filmmaker's crew is killed by a creature on a remote island. The Seaview goes to investigate the incident. One of the crewmen has a special interest in the mission as his father was one of the victims.
Episode: 3x09 | Airdate: Nov 13, 1966
Admiral Nelson wanders the Seaview and finds it abandoned except for Captain Crain and Chief Sharkey. He has no memory of what happened before or what the strange sounds over the intercom mean. Capt. Crane is also trying to kill him.
Episode: 3x10 | Airdate: Nov 20, 1966
Space aliens led by an entity which takes the form of a deceased WW2 officer acquaintance of Nelson's invade the Seaview, intending to reactivate an underwater atomic base to acquire its energy.
Episode: 3x11 | Airdate: Nov 27, 1966
Strange sounds and events begin to be reported on board the sub. While still coming to grips with the crews edginess, the Seaview encounters a strange 17th century warship that fires on the sub.
Episode: 3x12 | Airdate: Dec 4, 1966
A scientist in an underwater sea lab has created a new form of plant life. His twin brother, who can control him telepathically, is on his way there via the Seaview, with plans of using the new plant creatures for his own sinister purposes.
Episode: 3x13 | Airdate: Dec 11, 1966
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.
Episode: 3x14 | Airdate: Dec 18, 1966
While racing to the aid of a ship the Seaview suffers a critical engine failure. While doing repairs Admiral Nelson suffers a critical dose of radiation which affects him in a most unexpected way.
Episode: 3x15 | Airdate: Jan 1, 1967
While on a routine scientific expedition Capt Crane encounters a strange hybrid seaweed humanoid creature. Crane is captured by the creature and the crew of Seaview launch a desperate attempt to rescue Crane before his air runs out.
Episode: 3x16 | Airdate: Jan 8, 1967
The Seaview encounters a strange structure on the sea floor. Investigating they discover a German submarine from WW2. Surviving Germans on-board think the war is still being fought. And they have weapons on-board of unimaginable destructive power.
Episode: 3x17 | Airdate: Jan 15, 1967 (50 min)
A Norwegian scientific installation makes contact with an alien intelligence. The Seaview goes to investigate and ends up in a life and death struggle after the alien invades the sub.
Episode: 3x18 | Airdate: Jan 22, 1967 (50 min)
While on routine patrol the Seaview begins to hear strange noises coming from an undersea canyon. Investigating they discover the source of the noise and the power behind the destruction of a British fleet in the area 200 years before.
Episode: 3x19 | Airdate: Jan 29, 1967
Captain Crane discovers and captures a real mermaid. Everyone is interested in what the specimen might reveal until its mate turns up looking for revenge.
Episode: 3x20 | Airdate: Feb 5, 1967
The Seaview is tasked with transporting an Egyptian mummy from a New York museum for special secret testing. It becomes apparent very quickly not all is as it should seem, and soon a terrible threat is unleashed on the crew of Seaview.
Episode: 3x21 | Airdate: Feb 12, 1967
The Seaview is tasked with attempting a space probe launch from sea. To avoid interference a skeleton crew is manning the ship. While en route the ship encounters a strange object that unleashes a threat that could destroy Seaview and all on board
Episode: 3x22 | Airdate: Feb 19, 1967 (50 min)
While on patrol the Seaview is attacked and badly damaged by an unknown submarine. As the crew frantically work to save the vessel and themselves an even greater menace appears.
Episode: 3x23 | Airdate: Feb 26, 1967
The Seaview is following up reports of a strange island being sighted when it discovers a strange egg on the ocean floor. Everyone is puzzled and excited by the find until it hatches on board.
Episode: 3x24 | Airdate: Mar 5, 1967 (50 min)
The Seaview is tasked with moving a series of crates supposed to contain statues dating from the time of Atlantis. Something far more sinister is in the crates and Capt Crane is the only one in a position to save the ship.
Episode: 3x25 | Airdate: Mar 12, 1967
The Seaview investigates a strange cloud that seems to be the source of immense destruction around the world. The world has only 24 hours to live unless Seaview can crack the secret.
Episode: 3x26 | Airdate: Mar 19, 1967
Crane and the Admiral are on a mission to secure a new element that could be used to control the world. While exploring an undersea cave events occur that leave the admiral as the only survivor of the expedition and a changed man.
Season 4
Episode: 4x01 | Airdate: Sep 17, 1967
The Seaview is sent to stop an active volcano from erupting and causing a catastrophe. Accompanying them is Dr. Turner who's suppose to help them. But it turns out he has a different plan and that is to make the volcano erupt so he can acquire something that will make him immortal.
Episode: 4x02 | Airdate: Oct 1, 1967
A puppeteer comes on board to entertain the crew. But it is later revealed that his puppets are alive and they plan to take over the sub. That's when they replace the crew members with duplicates. Only Nelson and Crane are left to try and stop them.
Episode: 4x03 | Airdate: Oct 8, 1967
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.
Episode: 4x04 | Airdate: Oct 15, 1967
Aliens from the planet Centaur bring a capsule containing Commander Morton to Venus. They want to keep earth from invading their planet and kidnap Captain Crane in an attempt to bring the Seaview to their planet.
Episode: 4x05 | Airdate: Oct 22, 1967
When a top secret Neutron Bomb begins leaking radiation, Seaview crew men begin disappearing and those who haven't begin seeing things. The Seaview is racing the clock to fire or disarm the missile before it explodes.
Episode: 4x06 | Airdate: Oct 29, 1967
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.
Episode: 4x07 | Airdate: Nov 5, 1967
A scientist friend of Nelson has developed a device to control a rare white ape. The scientist's jealous assistant causes the beast to kill the scientist and the ape runs wild after being brought aboard Seaview causing destruction.
Episode: 4x08 | Airdate: Nov 12, 1967
A man named Alpha from 2823 sends 2 Collectors to bring Nelson to his time to add the Admiral to his collection of military officers. Chief Sharkey goes to the future to help while the Collectors wreak havoc on the Seaview.
Episode: 4x09 | Airdate: Nov 19, 1967
Captain Crane is attacked in the Flying Sub while looking for a mysterious sub pen. The Seaview's rescue attempts are hampered by a spy pretending to be one of the crew men.
Episode: 4x10 | Airdate: Nov 26, 1967
An alien plant takes over Admiral Nelson in a plan to turn the Seaview into a giant greenhouse where it can take over the world.
Episode: 4x11 | Airdate: Dec 3, 1967
The crew of the Seaview encounter Mr. Pem who can control time. Pem sends Nelson back in time to force the Admiral to let Pem use the reactor to power his device.
Episode: 4x12 | Airdate: Dec 10, 1967
While trying to stop a leaking nuclear missile, Nelson undergoes a personality change which endangers not only the Seaview, but the 11th Fleet.
Episode: 4x13 | Airdate: Dec 17, 1967
While trying to find the cause of some underwater pressure blasts, the Seaview encounters a race of Amphibians and Kowalski is transformed into one of them.
Episode: 4x14 | Airdate: Dec 31, 1967
The original Blackbeard takes over some of the Seaview crew including Kowalski to blow up a ship carrying King Solomon's Golden Throne. The remaining crew try to find a way to disable Blackbeard's power source.
Episode: 4x15 | Airdate: Jan 7, 1968
The Seaview is sent to stop a warhead on the ocean floor from detonating. But a leprechaun wants it to go off. So he tries to stop them. But his good twin brother tries to help them stop him.
Episode: 4x16 | Airdate: Jan 21, 1968
A lobster man arrives in a space craft claiming to be a friend but in reality he wants one of the nuclear rods to cause an explosion thus paving the way for an invasion.
Episode: 4x17 | Airdate: Jan 28, 1968
Crane receives a Mayday from the Seaview and finds no one on board except a UFO expert. The crew re-appears and announces they are going to fire nuclear missiles at Washington D.C.
Episode: 4x18 | Airdate: Feb 4, 1968
The Seaview rescues two scientist from a climate control project at the South Pole but something else is on the ship on a killing spree. The Seaview has to shut down the project before the world's climates change.
Episode: 4x19 | Airdate: Feb 11, 1968
The Seaview and an intelligence expert who is more than he seems, try to find a group that is blackmailing the world's nations for gold bullion. The submarine encounters gigantic creatures during their search.
Episode: 4x20 | Airdate: Feb 18, 1968
When Crane tests a new atmosphere to deal with extreme pressures, he turns into a Man Beast. Nelson races the clock to find a cure for Crane.
Episode: 4x21 | Airdate: Feb 25, 1968
The Seaview investigates why part of the Italian coast has become overrun with jungle growth. Meanwhile new crewman Keeler has 3 miniature silver faced men grow to human size and causes jungle growth to spawn all through the submarine.
Episode: 4x22 | Airdate: Mar 3, 1968
Investigating why the world's oceans are rising, the Seaview finds a race of Frost Men at the Polar Cap who are increasing the temperature and they want the submarines' reactor to help them leave the earth.
Episode: 4x23 | Airdate: Mar 10, 1968
While investigating the destruction of the fleet by a flying saucer, Nelson and Kowalski are captured by aliens. One of the aliens offers help to the Seaview crew to stop his people.
Episode: 4x24 | Airdate: Mar 17, 1968
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.
Episode: 4x25 | Airdate: Mar 24, 1968
Corpsman Mallory's 4th Dimension Machine causes Captain Crane to kill Admiral Nelson, but did he really? A hunted Crane tries to prevent the event from happening.
Episode: 4x26 | Airdate: Mar 31, 1968
Mr.Pem returns to help Admiral Nelson prevent the Seaview from exploding. Pem transports the submarine to 1780 where they encounter General Benedict Arnold and Major Andre.