For this one, I would be sailing a yacht to a buyer when I'm caught in a bad storm. This could play out a few different ways. I could be anchored off an island, and be taken from the water to become a mermaid, as their numbers are lessening, or I could be caught in a bad storm, and be tossed off by a rogue wave, which would necessitate a mermaid or merman saving me and altering me by magic of some kind to become a mermaid.
Im after someone with a decent imagination, male or female, that has at least part of the underwater world visualised, and wants more than just sex in their roleplays.
If this idea appeals to you and you want to know more, please let me know.