'Gamera vs. Deep-Sea Monster Zigra') is a 1971 Japanese kaiju film directed by Noriaki Yuasa, written by Niisan Takahashi, and produced by Yoshihiko Manabe and Hidemasa Nagata.

Back at Sea World, the dolphin trainer and the facility's scientists discover a way to break the alien's hypnotic control with sonic waves.

Thus, they manage to disable the Zigran woman, only to learn that she is actually an Earthwoman named Chikako Sugawara (Lora Lee in the English dubbed version), who had been in a Moon rover during the initial lunar attack and was captured and used by Zigra.

Wallace and Ishikawa employ a bathysphere in an attempt to wake Gamera, only to find that Kenichi and Helen have stowed away on board.

An electrical storm approaches the bay and a couple of lightning bolts revive Gamera, who stealthily takes the bathysphere from the sea floor when Zigra is asleep and returns it to the surface.

Gamera takes hold of Zigra, flies into the air with him and then drops him at high speed, slamming the alien monster onto the land.

Finally, Gamera kills Zigra by setting his body on fire with his flame breath, reducing the alien to ashes in a massive conflagration.

[1][4] Gamera vs. Zigra was released in Japan on 17 July 1971 as a double feature with the 1958 film Suzunosuke Akado: The Birdman with Three Eyes.

"[6] The review concluded that Gamera vs. Zigra "isn't nearly as much fun as it should be, but for those with a cheeky fondness for city-scale monster mashes, there are some fleeting pleasures.

"[6] In their scholarly book Japan's Green Monsters: Environmental Commentary in Kaiju Cinema, Rhoads and McCorkle offer an ecocritical assessment of Gamera vs. Zigra.

Rhoads and McCorkle argue that Gamera vs. Zigra possesses far deeper environmental appeals than the obvious ones present on the film's surface.