"If you and your friend return me to the sea, I can turn you into a merman and Caroline into a mermaid if you would like. I know of nothing else I can offer."
You consider the offer. It would be an adventurous escape into a new world. And as merfolk you and Caroline wouldn't have to worry about money anymore.
"There is a...what is your word for these things...a catch. I should explain that first..."