The next day, after some research on the internet, Marty decided Rad was getting turned on by the thrill of looking over the edge, and of forcing him to look over the edge alongside her. Indeed, she was an adrenaline junkie by nature. She had more adventure-filled stories than anyone else he knew, and in each one she was always pushing the limits of what was safe and responsible and sane, from cage-diving with saltwater crocodiles to walking along the wing of an airborne plane.

Understanding what drove Rad’s desire for erotic asphyxiation, and understanding that the deviant sexual activity was a lot more common than he’d previously believed, Marty felt a little better about his complicit participation. Yet choking was not his “thing” and never would be. Sex should be sensual and romantic, he thought, not violent. What they were doing could not be called lovemaking. They were fucking, plain and simple.

Which, for the time being, was fine with Marty—and fine, apparently, with Rad too.

“Who did that to you?” he asked her, surprised to find it bothered him that she had been with another man, despite the two of them acknowledging their open relationship.

“What does it matter, Marty?” she said. “You don’t know him.”

“Your tennis partner?”

“You’re cute when you’re jealous.”

“I’m worried for you, Rad.”

“You do the same thing to me!”

“I’ve never left bruises.”

“Would you prefer if I had him pull a plastic bag over my head?”

“I’d prefer if you gave up the damn fetish altogether.” He saw that his words had surprised and stung her, and he added, “Sorry. I guess I should check on the food.”

He went to the dinette, turned off the stove burners, and slid the food into the oven to keep warm. When he returned to the foredeck, Rad was plucking a small silver case from her clutch. She lit up a cigarette, blowing the smoke over her shoulder. “How was whatever you do here all day?” she asked him.

What little he’d told Rad about himself was this: he was a university professor on an indeterminate leave from teaching while he searched the seas for new species of marine life. This wasn’t far from the truth—he was simply leaving out the fact that the new species of marine life was merfolk. “Pip discovered a pod of whales that came by this way last year, only now they were two members short.”

“A regular Einstein, that girl.”

“She’s an excellent sonar technician.”

“Do you like her?”

“Excuse me?”

“You work together all day, just the two of you. Isolated out here…”

“Enough, Rad.”

“Why don’t you want to talk about her?”

“What you’re implying is nonsense.”

“What do you talk about with her other than sonar?”

Marty filled the bowl of his pipe with tobacco and lit up. “Clownfish,” he said around a mouthful of pungent smoke. “We discussed their breeding behavior today.”

“Breeding behavior, huh? Do clownfish have any particular fetishes?”

“No, but they have some peculiar fishishes.”