After a moment you realize the possibilities of what she means when she says "carry me to water and I will reward you" and realize that is obviously the better choice.
"How am I supposed to get you out of here without anyone stopping me? A guy walking through a store carrying a mermaid will kind of stand point..."
"Very carefully."
You sigh at the lack of help. You have the assistant-turned-mermaid put her shirt and skirt back on (how fortunate she was wearing a skirt!). You still need a way to hide the tail. You peek out of the changing room and just your luck - a large beach towel! You grab it without anyone noticing and do your best to cover her tail. You consider the situation for a moment and figure if nobody looks took closely you just might make it out of the store and to your car.
Another peek out the changing room door reveals nobody nearby so you scoop up ther maid and make a break for it...