Need to know the movie name please

This 1970s horror film is in color and is set in a quaint lakeside town. The townsfolk exhibit peculiar and suspicious behavior throughout the movie. A menacing black car makes frequent appearances, adding to the eerie atmosphere. As the story unfolds, it becomes evident that everyone in the town is involved in a sinister satanic or witch's cult. Towards the climax, a brave individual, either a man or a woman, manages to escape by rowing a small boat out onto the tranquil lake. However, their pursuit doesn't end there. The witches gather on the shore, and a chilling encounter takes place as someone from the water attacks them. These are the key elements I recall from the movie.