Clark is aboard the navy's newest atomic submarine in the South Atlantic when the sub is buffeted by an undersea earthquake. A giant lobster crawls out of a rift in the ocean floor that the quake creates and grabs hold of the sub. The lobster lets go of the sub and moves off but the sub is taking on water and can not surface.
Clark slips away, changes into Superman and leaves the sub via a torpedo tube and brings it to the surface and safety.
On a nearby island with a radar tracking station, the earthquake has activated a dormant volcano and a giant alligator climbs out of it and into the nearby water.
The radar tracking station is monitoring the imminent splashdown of a space capsule. The station notices their radar has been wrecked by the alligator and warns the capsule they can't assist in their landing. Fortunately for the astronauts in the capsule, Superman flies to their descending capsule and guides them down safely.
Superman encounters the giant lobster and alligator as they battle amidst the grounds of a carnival. Superman saves a tower from tumbling due to the creatures before using a ferris wheel to muzzle the alligator. Superman takes the creatures back to where they came from and seals up the hole that the lobster crawled out of.
At the Daily Planet, Perry asks Clark out for a lobster dinner but Clark say he's had his fill of lobster for the day.