As you continue to feel the merman's penis close to making you cum, you could also feel something else happening to you, while you began to feel something else happening to you. Your legs began to feel itchy, and you didn't want to let go, and scratch them, because it could distract you from not cumming in your own womb.
With that, the merman helped with scratching your legs, as he was penetrating you, and you began to notice small pink scales growing on your legs, while your pussy was being probed by his penis. You could feel the merman getting even closer, while scratching you at the same time as more pink scales form on your legs, and you could feel your own toes begin to fuse now that your scuba-flippers were off. That meant that you were close to becoming just like these merman, meaning you were becoming a mermaid.