Jenn quietly masturbated in the water, watching Oliver and Kelly have sex. As she did, she felt a strange tingle across her body, especially in her legs, but paid little attention to it. When they finished, she finished. Jenn she waited a few minutes longer to let her pulse return to normal. Then she slowly walked up out of the water and up the beach, doing her best Ursula Andress / Halle Berry impression, except naked. She made no effort to hide her naked body from Oliver and Kelly who were enjoying a post-coitus cuddle. She smiled at them, glanced at her neatly piled clothes, and realized there was no longer any point in wearing them. She lay down on the sand to sunbathe.
After a leisurely remainder of the morning, the trio explored the island further, gathered various fruits, and enjoyed dinner. Afterwards they sat around the fire talking about their lives, the uncertainty of their future, and whether they had any possibility of rescue. They agreed nothing made sense: the length of the day, the rise and set of the sun, the plant life on the island. It was as if they were in another world - which, unknown to them, they really were. When Jenn described her swim across the day, omitting some the more personal details.
"Did you see...us when you came back?" Kelly asked.
Jenn nodded. She felt a little embarrassed by her voyeurism, and guilt about her lust for Oliver. She didn't notice Kelly's smile.
When they went to sleep there was no hesitation for the three of them to huddle together for warmth. That night Jenn dreamed of swimming across the bay again, but this time as an azure fish tail mermaid. Then she encountered Oliver as a merman with a dark blue tail and they made love underwater.
Jenn woke up in the morning to find Oliver's arms around her, his morning wood pressing against her. He noticed her stirring and wished her a Good Morning. They got up, Jenn trying her to shake her dream from her mind and to not stare at his erection.
"Where's Kelly?" Jenn asked.
"She went for a walk," answered Oliver.
Jenn suggested they find breakfast. Heading into the jungle, Jenn described the sweet and juicy fruit she had found across the bay yesterday, which she was craving more of.
"I think I know exactly what you're talking about. Kelly and I had some for breakfast yesterday." Jenn didn't make the connection.
Oliver lead her what was indeed the same type of tree. Jenn eagerly began to eat one of the fruit. Jenn was already on her third fruit by the time Oliver had finished his first. She was heedless of the juice runing her chest until Oliver began to lick it off, to Jenn's great surprise. When he had his arms around her and started to tease her nipple with his tongue, Jenn felt guilt and panted, "What about Kelly?"
"This was her idea," assured Oliver.
Confused but ecstatic, Jenn kissed Oliver hungrily. When she felt his hand began rubbing her pointed ear, she couldn't hold back any longer. "Fuck me" she commanded. "But not here..."
Jenn took Oliver by the hand and led him back to the beach. Her mind swirled with confusion. Was Oliver telling the truth? Since when did she have pointed ears? Why did she have such a strong desire for sex in such a specific location? Her legs tingled with anticipation.
Oliver though Jenn was bringing him back to the shelter, but she took him right past that down the sand and into the water. Once they were waist deep, Jenn stopped and turned to him. "Here" she begged, pressing her body against his, kissing him passionately.
"In the water? Are you sure" Oliver asked.
"Yes. I can't explain it, but it has to be here." She wrapped her legs around him, and guided him into her. She hung onto him as he grabbed her firm ass and began thrusting. With each thrust Jenn felt her legs weaken and her orgasm build. She didn't know it, but the aquatic sex was the finally step to trigger her transformation into a mermaid. The mermaid of her dream, and of the poster that had sent the three of them here.