(First Aired: December 25, 1966)
Screenplay by: Keisuke Fujikawa
Directed by: Toshihiro Iijima
Science Patrol has opened up their new Undersea Center and will take Mr. Yoshimura, the President of the Public Science Corporation, there to activate the Center’s switch with the 200th guest at the opening celebration coming along for the tour. The 200th guest happens to be a young American girl named Jenny with her father following a bit behind her. With that, the guests head out with Muramatsu, Fuji, and Hoshino to the Undersea Center via the submarine S25. Nobody notices something moving underneath the seafloor that smashes the base’s oxygen pipeline though.
Soon, the sub reaches the Undersea Center, and Mr. Yoshimura turns on the switch. Fuji then heads back to pick up the press group, but as the sub leaves the Center behind, a massive drill bursts from the seabed and begins to punch a hole into the Undersea Center’s hull. The people inside feel the violent shakings caused by the mystery attacker, leading Muramatsu to try contact Fuji. However, he can't make contact with her, thanks to the drill damaging communications, which is made more problematic by the fact that Fuji’s now spotted the destroyed oxygen pipeline. Hoshino then reports that the docks are flooding as well!
Back on land, Hayata, Arashi, and Ide are at the monitor room and have noticed the oxygen line’s damages when the pipeline monitor starts acting funny. They are unable to make contact with the Center’s communications either, so they switch to their Science Patrol communicators. Muramatsu informs them of the dock’s mysterious destruction, which prevents any hope of a submarine docking rescue. Arashi suggests that they call in the Tortoise from the Ocean Research Center as it can create a passage of escape by latching itself to the Center. However, to penetrate the Center’s extra-durable walls, they’ll need a new invention from Ide.
In the Center, Mr. Yoshimura and Muramatsu pass the time with a game of cards while Hoshino keeps Jenny cheered up. Mr. Yoshimura is growing impatient though. And although Ide has finished his wall-cutting invention back on land, things are getting worse underwater as Jenny descends into unconsciousness from lack of oxygen and the main room begin to flood. Everybody puts on oxygen tanks, as they head to the next floor of the Center. But Muramatsu is without one, as he used the last one to keep Jenny conscious, to which he accepts.
Back on land, the rescue mission begins with Ide and Fuji in the Tortoise and Hayata and Arashi in the S25. They arrive quickly, but Arashi spots a monster swimming their way. S25 moves in to deal with the sea monster – Gubila, a narwhal-like beast with turtle-like flippers and a drill for a nose, indicating it was behind the attack on the Center. A few torpedoes are enough to turn Gubila’s attention to the S25 while Fuji prepares the wall-cutter. At this point, Muramatsu and the rest have reached the top floor of the center, where the wall-cutter has been placed. The invention is ready and the Tortoise latches on, opening a hatch for everyone to get through. Everybody is saved, but Gubila has managed to smash the S25, knocking Arashi unconscious. This gives Hayata the opportunity to become Ultraman!
Ultraman follows Gubila through the water, so the monster begins drilling through an undersea cliff. Ultraman follows Gubila into the tunnel, which eventually takes the two giants onto land. Ultraman and Gubila proceed to fight, and Gubila’s drill nose gives Ultraman a difficult time. Eventually, Ultraman manages to karate chop the drill off Gubila's face. As Gubila squeals in pain, Ultraman fires a Specium Ray, destroying the narwhal-like beast. With that, Ultraman flies off. Meanwhile, the Tortoise lands safely and Jenny is reunited with her relieved father. Elsewhere, Arashi has regained consciousness and finds that Hayata has fixed the S25 and is piloting it back to land as they speak.
Tropes:
- Enclosed Space: The Undersea Science Center becomes one after Gubila destroys the oxygen line and the Center's dock, forcing Science Patrol to find a way to rescue the people inside.
- Sea Monster: Gubila is one, with its subtitle being "Deep Sea Monster", though Ultraman fights it after it's tunnelled to the surface.
- This Is a Drill: Gubila's nasal horn is a drill, which it uses to destroy the Undersea Science Center's oxygen line, and gives Ultraman a hard time with it during their battle.
