The Giant Behemoth (1959)

Behemoth, the Sea Monster (1959) is an American-British science-fiction film co-production. Originally a story about an amorphous blob of radiation, the script was changed at the distributor's insistence to a pastiche of The Beast from 20,000 Fathoms (1953), though elements of the original concept remain in the early parts of the film and in the "electric eel" power of the titular monster. The script was written by blacklisted author Daniel James under the name "Daniel Hyatt," with Eugène Lourié co-writing as well as directing. Released in the United States as The Giant Behemoth, the film starred Gene Evans and André Morell. It was distributed by Allied Artists Pictures.


Dead fish by the thousands begin washing up on the shores of Cornwall, England, and finally an old fisherman is killed by something which has left him covered with radiation burns, his dying word being "behemoth". An Anglo-American team of scientists are dispatched from London to investigate, and discover the dead fish are also radioactive. Further investigation reveals a large, glowing animal swimming below the surface of the sea, and on another night it comes out and "burns" a farmhouse and its occupants, leaving footprints the length of a police car. From a picture of one print, a paleontologist determines the animal is a [fictional] Paeleosaurus that can project electric shocks and is saturated with radiation. The dinosaur enters the River Thames and surfaces and attacks the city of London. The scientists realize that if it is destroyed by conventional military weaponry, a large amount of radioactive contamination will be released. The military then concludes to use a mini-submarine capable of shooting a torpedo missile with enough additional radioactivity inside the warhead to overdose the behemoth and destroy it. The American scientist and one of the younger Cornish fishermen, boyfriend of the daughter when the first man was killed take the mini-sub out, aimed at the pest and successfully shoot the behemoth.

From Wikipedia

THE GIANT BEHEMOTH
EUGENE LOURIE  (1959)
ALLIED ARTISTS
USA
79 MIN