"Maybe you just need to dry off?" you suggested.
"That makes sense" said Lydia. "Can you carry me to my room?"
You pick her up and carefully make your way to the back door. Lydia helps with the sliding door. You make your way to Lydia's room where she directs you to a closet with towels. You lay her down on her bed on one towel then take the other towel to dry yourself off.
"This still kind of strange" said Lydia. "It feels just like running a towel down my legs to dry off after a swim meet, but I've got a mermaid tail instead of legs." She runs hand along her tail, feeling it in a way you find sexy, whether that's intended or not.
After she's finished drying off, Lydia frowned. "I haven't started changed back. Maybe there's more to your wish that's keeping me like this?"
You think back to your encounter with the genie. "I guess the wording to the genie was vague. I said temporarily, but I didn't say how long."
"But you've fulfilled your fantasy, right?" asked Lydia.
"Does doing something once count as fulfilling a fantasy? That could be open-ended, especially with a tricky genie..."
"Maybe it's something more specific? Did you fantasize about having sex somewhere specific? Or a certain position?"
You think about it for a moment. "I've fantasized about sex on the beach."
"That makes two of us" Lydia says without thinking, then blushes a little.
"With you as a mermaid?" you ask, your curiosity piqued.
"Maybe..." she replies. "Yes. And as a human too." After a pause she adds "We should try that."
"In the shower, although not with you as a mermaid because that wouldn't work. Maybe after one of your swim meets, or after sneaking into the school pool for some late night skinny dipping."
"Go on..." said Lydia. You could tell she's getting excited. The two of you have never discussed your fantasies before.
You toss your towel aside and approach Lydia. "Right here on your bed."