"Sure why not" you say
Amy helps you put on the polo suit as you have to really try not to rip them when putting them on. After you put on the polo suit water tights and swim cap she helps you put on the tail. When the tail is on she goes into the bathroom to change as you are waiting you feel pressure build up in your chest. When you look down you see 2 mounds of flesh growing from your chest you then reach for your cock which you can feel shrinking now. When the transformation is complete amy walks out of the bathroom.
"Looks like we went to the same place for our costumes" she said
Then you notice she looks exactly like a succubus.
"So you mean to say these costumes can change us" you said.
"Yes they can" said Amy
You couldn't believe it then you start to feel dry and remembered that mermaids can last as long outside of water as humans can.
"Can you help me to the tub or help me get this costume off Amy" you ask
"I'll help you to the tub you look so cute as a mermaid" Amy said
Amy helps you to the tub and you start the water. Now you...