"Are you just going to stand there and leave this poor mermaid alone?" asked Sharon.
John smiled. "Of course not." He climbed into bed and wrapped his arms around Sharon. They pressed their lips together in a passionate kiss.
"Have you ever fantasized about making love to a mermaid?" asked Sharon.
"Yes" admitted John "but one that looked like you."
They kissed again and Sharon could feel the bulge of John's pants against her. They continued to kiss as they worked to remove each other's clothes. Soon they were laying naked together, except for Sharon's tail.
"I guess it has to come off now" said John with obvious disappointment in his voice.
"Not it doesn't" said Sharon and she guided John's hand to the slit in the costume.
John's eyes lit up with joy and he mounted Sharon and slid into her. Their usual rhythm proved difficult with Sharon's legs bound together by the tail, but the experience caused a warm, pleasant sensation in her lower extremities. Soon Sharon realized she was absentmindedly flicking her tailfin in rhythm with John's thrusts. The waves of pleasure built slowly, but the happy couple were lost in the moment. Finally John reached his peak and erupted into Sharon before collapsing on the bed next to her.
Sharon briefly disappointed. After all their years together they had learned pretty well how to climax together. Maybe the tail wasn't so great an idea after all, at least for her. Besides, both her legs had fallen asleep, presumably from the constraints of the tail. Still, she was close to the edge and could probably finish herself...
Before she could try, the orgasm hit her like a tsunami. Her back arched and she let out a deep moan of pleasure that startled John.
"Sharon, are you okay?"
Sharon couldn't immediately respond. It felt the wind had been knocked out of her, so powerful had the orgasm been. But she could feel her legs again as her tail flopped a little on the bed, almost like it had a mind of its own.
"Sharon?"
"I'm...oh my...I'm okay. That was just...intense, to say the least."
John curled up with his wife, wrapping his legs around her tail.
"This tail is so well designed that I can feel you legs like they're against my skin" observed Sharon.
John ran his hand down Sharon's stomach, feeling the smooth transition from skin to scales, like there was no seam at all. Sharon giggled. "That feels good."
Sharon was enjoying herself, but John felt worried. The tail had been good, but at first it still felt like a tail. Now it felt more realistic - maybe too realistic. He felt around to the back of the tail, trying to find a zipper to reassure himself.
"There was a zipper on this right? asked John.
"Of course, it was...." Sharon's cut herself short as her hand touched smooth scales where before there had been a zipper. Feeling around her waist Sharon could find no seam. Finally she felt for the slit left in the tail that had allowed them to have sex with the tail on. She only found her own slit. Willing herself to do the impossible, Sharon bend her tail up, curving it in a way not possible if she still had knees.
"John, it's not a costume anymore - I'm a real mermaid."