"The thing you have to understand," she explains, once the two of you are alone in (thankfully) cleaner water, "is that mermen are not born. They have to be transformed from landsmen, like that mermaid tried to do to you. So most of a mermaid's life is spent trying to lure just the right one."
"I'm not sure I can--" you start, looking down at your unfamilar shape.
"Nonsense," the frog-girl replies. She puts her hands on your now narrow waist. "With a form like that, you'll find it easy. You just have to haul yourself up on a rock and wait. The other mermaids will automatically trust anyone who's doing that."
She pulls on your arm, leading you to a particular set of rocks.