Dare the Devil (1969)

This is the story of David Keller, young, confused and uncertain. On a trip to the beach with his fiancée, the two are attacked by a group of hoodlums in dune buggies and although David fights them with every ounce of his strength, he is unable to prevent the rape of his girl. Disillusioned and frustrated by his fate, he has a chance meeting with Molly, attractive and old enough to be his mother, and decides to live with her for a while. Here he has his first affair and his first taste of liquor and the lusts and passions of life. There is a lively and entertaining night club sequence. Then comes Molly’s teen-aged daughter and more complications. This is an explosive, controversial action drama of today’s youth and their problems. (from: http://templeofschlock.blogspot.de/2010/07/endangered-list-case-file-73.html)

Unfortunately the movie Dare the Devil is not yet available on HBO Max.