As you lay back and allow Mark to take control, you can't help but feel a mix of excitement and guilt. Despite your reservations, the allure of the merman is too much to resist.
Mark begins to pleasure you, his skilled hands and mouth exploring every inch of your body. You can feel yourself becoming more and more aroused, and you can't help but let out soft moans of pleasure.
Mark eagerly kisses you and moves his hands down to your thighs. He gently spreads your legs and begins to massage your inner thighs, making you gasp with pleasure.
His touch is electric and you can feel yourself getting more and more turned on. You wrap your arms around him and pull him closer, kissing him deeply as he continues to pleasure you.
As the two of you make love, you can feel a strange sensation taking over your body. Your skin begins to tingle and shimmer, and you can feel your body transforming even more. You have become even more of a mermaid, with a fishtail now replacing your legs.
Mark looks at you in amazement, clearly impressed by your transformation. "You are even more beautiful now," he says, admiring your new form.
You are both lost in the moment, and you forget all about your boyfriend back on land. You give yourself over to the pleasure that Mark is giving you, and the two of you make love for what feels like hours.
When it's all over, you lay in Mark's arms, feeling exhausted but incredibly happy. You know that you have cheated on your boyfriend, and that you are now even more of a mermaid than before. But in this moment, none of that matters. All that matters is the pleasure that you have just experienced, and the connection that you now have with Mark.