"So...how much longer is the full moon for?" you ask.
"Long enough" replies Katie. She kisses you deeply, your bodies pressed against each other. One of her hands travels down your body to your cleft. You revel in the sensation.
After a moment, Katie breaks the kiss and pushes you away. For a second you worry she's changed her mind, but then you notice the smile on her face. She flicks her tail at you and swims off. What a tease!
You give chase, but Katie is more familiar with swimming with a tail than you. Then you manage to catch up with her; you suspect she let you catch her. A brief kiss then she darts off again and you continue pursuit. The second time you catch up, you manuever to grab her from behind. Your tails rub and the feeling is electric. You reach around her body to grab her breasts and gently fondle them. She moans with pleasure. She reaches a hand back and feels for your cleft. The sensation causes you to let go. And she swims off again.
The game of underwater tag continues, with kisses and touches keeping you both excited. Soon you find yourselves in shallow water. Tiring, you ride the surf onto the beach. You roll over on your back, taking deep breaths from the exertion of so much swimming - far more than you're used to. You run a hand along your tail, still amazed at your new body. The surf splashes against your fins.
Another small wave rolls in, bringing Katie with it. It carries her almost perfectly to on top of you.
"Tired already?" she asks.
"Only too tired to swim right now. Plenty of energy left for other things..." you reply.
You pull her into a kiss. Your breasts and mermaid tails press against each other. Katie breaks the kiss and begans kissing her way down your neck then to your breasts. You're pretty sure you know where this is headed and look forward to every minute of it...