The two met in 1970 when the New College of Florida student was on his first freelance photography assignment. He was supposed to take pictures for a book about Sarasota's Floridaland—one of those hokey roadside attractions that populated the Sunshine State before multimillion-dollar theme parks pushed them out. Soon, however, he was sidetracked by the dolphin.

Some would call Brenner, who had sex with Dolly more than four decades ago, a pervert or an animal abuser or, at the very least, a damaged man. But to this day, Brenner, who is now the subject of a documentary, describes the encounter as a beautiful, almost spiritual experience.

Dolly swam to the other side of the tank when the unfamiliar human with horn-rimmed glasses and shoulder-length curls first jumped in. She eventually came around, says Brenner, who photographed the dolphin for nine months. Once, as he was rubbing her back, Dolly flipped over to present her genital slit. Later, she started rubbing her teeth on the photographer's arm in what he describes as an erotic way. When he wouldn't give her what she wanted, Dolly would retaliate by pushing him 12 feet underwater.

"Female dolphins are very assertive about their sexuality," Brenner told me. "They don't have any inhibitions about expressing it, whereas other animals are passive, or at least just receptive."

In his telling, Brenner has always been attracted to animals. As a child, he says, he was molested by his psychologist. Around the same time, his dad took him to see a Disney film called The Shaggy Dog. He got an erection even though he was only five, which he now calls a defining moment of his life. His zoophilia started in earnest a few years later; when he was 11 or 12, Brenner had sex with the family poodle, although he says he felt dirty afterward.