Ebirah, Horror of the Deep (1966)

After her son Yata is lost in the South Seas, Kane consults a psychic medium, who assures her her son is still alive. With this information, Yata's brother Ryota tries to convince the authorities to resume their search for his brother. When they refuse, Ryota decides to take matters into his own hands. When he sees a flyer for a dance endurance marathon with a boat as the grand prize, Ryota tries to enter, only to find he is too late. When they hear Ryota is looking for a boat, two contestants, Ichino and Nita, decide to show him all the boats at the dock. They climb aboard one specific boat, the yacht called Yahlen, which is seemingly empty. However, they are confronted by Yoshimura, who is armed with a gun and claims to be the ship's owner. Yoshimura tells the three they can stay for the night, but need to leave by morning. All the men go to sleep inside the yacht, but when they awake in the morning they find they are adrift on the open ocean, with Ryota having taken command of the craft to try and find his brother. They then overhear a radio report saying that the yacht has been stolen, and learn that Yoshimura is a thief who recently robbed a bank and was simply hiding on the Yahlen.

After several weeks at sea, the Yahlen comes upon a severe typhoon, which batters the ship before a huge lobster claw breaks the surface and cuts the ship in two. The next morning, the four men find themselves washed ashore on Letchi Island, which seems to be uninhabited. The men climb a mountain to reach the interior of the island, and immediately find a sword. While they worry that the island may not actually be uninhabited, the men use the sword to cut through the brush in the jungle and cut down fruit from the trees. After wandering through the jungle, the men come upon a dock, where a ship is seemingly delivering a load of cargo to a group of armed men. The cargo is taken out of the ship, and revealed to be a group of Infant Islanders bound in chains. As the armed men begin to escort the Infant Islanders away, two of the prisoners escape and try to reach a boat. A machine gun in a nearby watchtower opens fire on them, but cannot hit them. One of the armed men, Captain Ryuii, orders the guns to stop firing, declaring "Ebirah" will take care of the escaped prisoners. As the two escapees row out to sea, a huge claw erupts from the water and destroys the boat. Soon, a huge crustacean surfaces and uses the claw to impale the two men and eat them before diving back under the waves. In the confusion, one of the islanders slips away and escapes into the jungle.

When the four men realize the inhabitants of Letchi Island are far from friendly, they retreat back into the jungle, where they run into the escaped Infat Islander. After they convince her they mean no harm, she introduces herself as Dayo, a native of Infant Island. She reveals that the armed men are a terrorist group named the Red Bamboo, who frequently abduct natives of Infant Island to use them as slaves for their operations on Letchi Island. When a group of Red Bamboo soldiers approach, the five run away until they find a cave inside a cliff at the edge of the island. They hide inside, and the Red Bamboo give up the search. As the four men debate their next move, Dayo begins praying to Mothra, who is unfortunately asleep at the moment and cannot hear her people's prayers. When the men look at the bottom of the cave, they notice Godzilla lying motionless. After listening closely, they hear his heartbeat and realize he is alive. Not willing to stay in the same cave housing Godzilla, the five decide to try and infiltrate the Red Bamboo's base on the island. Hiding behind a makeshift bush made from leaves and sticks, the five slowly approach the base and avoid detection from a guard tower. Once they reach the door, Yoshimura uses his lockpicking skills to bypass the lock and allow them inside. The five slip past guards and eventually reach a strange door. Yoshimura picks the lock and goes inside, but realizes that within the door is a nuclear reactor. Yoshimura then determines that this installation is a factory that manufactures heavy water, a substance used for the production of nuclear weapons. As they explore more of the base, they take some gas bombs and copper wire with them. But then, they find themselves face-to-face with Ryuii and his men. Yoshimura tells the others to give up and surrender, but quickly tosses a gas bomb at the Red Bamboo guards, allowing himself and the others to escape.

Outside the base, two of the men pose as Red Bamboo scientists carrying metal panels, with the others hiding between them. However, the Red Bamboo guards notice and catch on, and open fire with their machine guns. The five all scatter, with Yoshimura, Ichino and Dayo escaping back to the cave, while Nita is captured by the Red Bamboo. Ryota gets his leg tangled in a rope attached to a balloon, which floats into the air and carries him off the island. Back in the cave, Yoshimura and the others form a desperate plan to stop the Red Bamboo and hopefully give them a chance to escape the island: wake up Godzilla. They place the copper wire they took from the base near Godzilla's head, then run it to the outside of the cave, where they place the sword to act as a crude lightning rod. Once a thunderstorm finally passes overhead, lightning strikes the sword, sending an electrical current down the wire and to Godzilla. Godzilla stirs and finally awakens before breaking free from the cave and roaring mightily. Godzilla begins walking toward the coast, but is confronted by Ebirah, who initiates a battle with Godzilla. Godzilla begins throwing rocks at Ebirah, who throws them back and forth at Godzilla until one strikes Godzilla in the knee. Godzilla charges into the water and begins grappling with Ebirah, before blasting the water with his atomic breath, boiling Ebirah alive and forcing him to retreat. Victorious, Godzilla comes back ashore and heads for the interior of Letchi Island.

The balloon carrying Ryota finally touches down on Infant Island, right in the middle of a native ceremony attempting to awaken Mothra. There, Ryota finds Yata, who had been taken in by the Infant Islanders after his shipwreck. Ryota tells the islanders about the activity of the Red Bamboo, to which the Shobijin reply that they are well aware. Yata, not willing to let the islanders continue being persecuted, offers to go to Letchi Island with Ryota to rescue the islanders. The Shobijin thank them, and tell them to construct a large net while on the island and wait. The Infant Islanders load up a boat with supplies, and Ryota and Yata are sent on their way. Back on Letchi Island, Nita has been thrown into a prison with the Infant Islander slaves, who are being forced to create a yellow juice from fruits found on the island. One of the natives explains to Nita that this juice is used by the Red Bamboo's ships to hold off Ebirah so they can freely enter or leave the island's waters. This gives Nita an idea; he tells the others to use only the leaves of the fruit to produce a fake liquid. The others agree and quickly begin enacting Nita's plan.

Godzilla takes up residence on a cliff, where he sits down and nods off. Yoshimura, Ichino and Dayo try to pass by Godzilla, but he awakens before Dayo can get to safety. Godzilla begins staring curiously at Dayo, but is suddenly attacked by a Giant Condor. Godzilla briefly battles the colossal bird before setting it ablaze with his atomic breath and sending it crashing into the water below. Godzilla roars victoriously before turning his attention back to Dayo, whom he continues to admire. The Red Bamboo send several fighter jets to attack Godzilla, which the kaiju easily destroys. However, the confusion buys Dayo time to escape with the others. Godzilla decides to retaliate by assaulting the Red Bamboo's base. As Godzilla approaches, Ryuii and the Red Bamboo commander decide to flee the island and order their men to trigger their base's self-destruct mechanism. Godzilla easily breaks through their defenses and begins kicking the nuclear reactor, causing the Red Bamboo's base to collapse. One Red Bamboo scientist manages to trigger the self-destruct before he is crushed by debris, leaving Yoshimura to desperately attempt to disable it. When he cannot reach the override button, Yoshimura and the others decide to flee toward the edge of the island. Ryuii, the commander and the Red Bamboo's remaining men take the slaves' latest batch of yellow juice and place it aboard their ship, unaware the liquid is fake. As their ship begins leaving the island's waters, Ebirah surfaces and destroys the ship, killing everyone aboard. Upon seeing Ebirah, Godzilla re-enters the island's waters and begins a second battle with Ebirah. Ebirah uses his claws to pull Godzilla underwater, but Godzilla smashes Ebirah's face with a boulder and swims back to the surface. Ebirah tries to grapple with Godzilla again, but Godzilla bites down on his claw and tears it off. He then bites Ebirah's other claw and bites it off as well before blasting the water with his atomic breath, boiling Ebirah alive once again. Thoroughly defeated, Ebirah swims away as Godzilla taunts him with his severed claw.

Ryota, Yata, Nita, Ichino, Yoshimura and Dayo all meet up and help the Infant Islanders escape and build a giant net as instructed by the Shobijin. True to their word, the Shobijin soon arrive on the back of Mothra, telling everyone to stand inside the net. When Godzilla sees Mothra flying overhead, he comes back ashore and tries to instigate a fight with her. Not wanting to waste time fighting Godzilla, Mothra knocks him over with her wing and grabs the net holding the islanders and the others, then flies away. As everyone looks back to the island, they remark that Godzilla saved their lives and begin to call to him, warning that the island will soon explode. Godzilla watches Mothra fly away for a few moments, then dives into the water just as the island is consumed by a nuclear explosion. Godzilla surfaces and roars, causing everyone to celebrate when they realize he has escaped.