It Came From Beneath The Sea. 1955.
A giant radioactive Octopus rises from the sea and terrorizes a North American coast.
Another creature feature headlined by lead actor Kenneth Tobey that is left to pick up the pieces when Atom Bomb testing releases a Octopus from it's lair, grows in size and becomes something big and scary. Ray Harryhausen was able to create the stop-motion effects for the sea monster that has a abnormality which is easily noticed, but because it's a Harryhausen creation it can be ignored. This was better than expected to be.
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