The Monster of Piedras Blancas (1959)

 

The main thing I remember was the 10-year-old boy with a leg brace. He was the director's son. He finds a dime on the ground, goes into the store to spend it and finds the shop owner dead. He runs--hopping two steps in his good leg for ever one with his bad one--to his mother at the graveside service for the monster's last victim. 

"He didn't have any head!"

It was painful seeing a child suffering from the effects of polio. It gave his character a backstory. The little fellow had been through enough without finding a headless body. He appeared in another movie his father made and went on to direct a few himself. 

A creature-from-the-black-lagoon-like fish man terrorizes a coastal community. The lighthouse keeper had been feeding it. I don't know if that was a mistake on his part.

With Les Tremayne and Don Sullivan. 

I watched it on Pub-D-Hub which means it's public domain and must be available on a lot of other streaming channels.