Once upon a time, Marina Johnson, a 49-year-old housewife who was born in South Carolina and lives in Florida, was a Sunday school teacher. She sang in the church choir. Her husband (ex-husband now) was a deacon. For Marina, doing what you're about to see her do was the furthest thing from her mind. "No way," she said. "I didn't even have an opinion about girls who did porn because I never thought about it." One divorce, one happy marriage and 19 years later, Marina has done a complete 180. Those D-cup tits? Yeah, they're fake, they're very nice, they have pointy nipples and Marina never would've gotten them if she were still married to her ex. As for sucking and fucking a total stranger on-camera? No way. "I recently had sex at a swingers club," she said. "I gave my man a BJ and then climbed on for a ride while the whole room of people watched. What a rush!" If you met Marina Johnson, you'd think she was a classy Southern belle with a subtle sexuality. Well, there's absolutely…