1971/21: A Bay of Blood aka Twitch of the Death Nerve 1971

 Trailer:

 Watch movie:

https://youtu.be/Jakf-B3FXKY?si=aXYrsK0EDHpLQoUm 

https://en.wikipedia.org/wiki/A_Bay_of_Blood

https://www.moriareviews.com/horror/twitch-of-the-death-nerve-1971-a-bay-of-blood-carnage-ecology-for-a-crime-antefatto.htm 

https://eofftvreview.wordpress.com/2019/01/19/antefatto-1971/ 

http://www.1000misspenthours.com/reviews/reviewsn-z/twitchofthedeathnerve.htm