Behemoth the Sea Monster (1959)

The dumping of radioactive waste in the ocean disturbs a prehistoric monster than can project electric shocks and radioactive beams. After terrorizing the English coast, it is discovered that if the creature is destroyed with conventional weaponry it would spread a dangerous amount radioactive contamination over the entire country, with this fact preventing the military from attacking the monster as it nears London.

Gene Evans, André Morell, John Turner

1959, B&W, 80 minutes